stop ignoring ruff rule B904 (#22641)

pyproject.toml

@@ -35,9 +35,7 @@ exclude = [
 line-length = 88
 
 [tool.ruff.lint]
-ignore = [
-  "B904",  # Within an `except` clause, raise exceptions with `raise ... from err|None`
-]
+ignore = []
 select = [
     "B",  # flake8-bugbear
     "E",  # pycodestyle errors

src/olympia/abuse/serializers.py

@@ -239,14 +239,14 @@ class AddonAbuseReportSerializer(BaseAbuseReportSerializer):
 
         try:
             is_value_unknown = value not in reversed_choices
-        except TypeError:
+        except TypeError as exc:
             # Log the invalid type and raise a validation error.
             log.warning(
                 'Invalid type for abuse report %s value submitted: %s',
                 field_name,
                 str(data[field_name])[:255],
             )
-            raise serializers.ValidationError({field_name: _('Invalid value')})
+            raise serializers.ValidationError({field_name: _('Invalid value')}) from exc
 
         if is_value_unknown:
             log.warning(

src/olympia/abuse/views.py

@@ -225,9 +225,9 @@ def cinder_webhook(request):
 
         try:
             cinder_job = CinderJob.objects.get(job_id=job_id)
-        except CinderJob.DoesNotExist:
+        except CinderJob.DoesNotExist as exc:
             log.debug('CinderJob instance not found for job id %s', job_id)
-            raise ValidationError('No matching job id found')
+            raise ValidationError('No matching job id found') from exc
 
         if cinder_job.resolvable_in_reviewer_tools:
             log.debug('Cinder webhook decision for reviewer resolvable job skipped.')

src/olympia/activity/utils.py

@@ -141,12 +141,12 @@ def add_email_to_activity_log(parser):
     uuid = parser.get_uuid()
     try:
         token = ActivityLogToken.objects.get(uuid=uuid)
-    except (ActivityLogToken.DoesNotExist, ValidationError):
+    except (ActivityLogToken.DoesNotExist, ValidationError) as exc:
         log.warning('An email was skipped with non-existing uuid %s.', uuid)
         raise ActivityEmailUUIDError(
             'UUID found in email address TO: header but is not a valid token '
             '(%s).' % uuid
-        )
+        ) from exc
 
     version = token.version
     user = token.user

src/olympia/addons/admin.py

@@ -465,8 +465,8 @@ class AddonAdmin(AMOModelAdmin):
             try:
                 if lookup_field in ('slug', 'guid'):
                     addon = self.get_queryset(request).get(**{lookup_field: object_id})
-            except Addon.DoesNotExist:
-                raise http.Http404
+            except Addon.DoesNotExist as exc:
+                raise http.Http404 from exc
             # Don't get in an infinite loop if addon.slug.isdigit().
             if addon and addon.id and addon.id != object_id:
                 url = request.path.replace(object_id, str(addon.id), 1)
@@ -596,8 +596,8 @@ class ReplacementAddonForm(AMOModelForm):
         except forms.ValidationError as validation_error:
             # Re-raise the ValidationError about full paths for SITE_URL.
             raise validation_error
-        except Exception:
-            raise forms.ValidationError('Path [%s] is not valid' % path)
+        except Exception as exc:
+            raise forms.ValidationError('Path [%s] is not valid' % path) from exc
         return path
 
 

src/olympia/addons/decorators.py

@@ -23,8 +23,8 @@ def addon_view(f, qs=Addon.objects.all, include_deleted_when_checking_versions=F
                     addon = qs().get(id=addon_id)
                 elif lookup_field == 'guid':
                     addon = qs().get(guid=addon_id)
-            except Addon.DoesNotExist:
-                raise http.Http404
+            except Addon.DoesNotExist as exc:
+                raise http.Http404 from exc
             # Don't get in an infinite loop if addon.slug.isdigit().
             if addon.slug and addon.slug != addon_id:
                 url = request.path.replace(addon_id, addon.slug, 1)

src/olympia/addons/fields.py

@@ -230,8 +230,10 @@ class SourceFileField(serializers.FileField):
                 mode = 'r:bz2' if ext == '.bz2' else 'r:gz'
                 with SafeTar.open(mode=mode, fileobj=data):
                     pass
-        except (zipfile.BadZipFile, tarfile.ReadError, OSError, EOFError):
-            raise exceptions.ValidationError(gettext('Invalid or broken archive.'))
+        except (zipfile.BadZipFile, tarfile.ReadError, OSError, EOFError) as exc:
+            raise exceptions.ValidationError(
+                gettext('Invalid or broken archive.')
+            ) from exc
 
         return data
 
@@ -262,8 +264,10 @@ class VersionCompatibilityField(serializers.Field):
         for app_name, min_max in data.items():
             try:
                 app = amo.APPS[app_name]
-            except KeyError:
-                raise exceptions.ValidationError(gettext('Invalid app specified'))
+            except KeyError as exc:
+                raise exceptions.ValidationError(
+                    gettext('Invalid app specified')
+                ) from exc
 
             existing_app = existing.get(app)
             # we need to copy() to avoid changing the instance before save
@@ -278,10 +282,10 @@ class VersionCompatibilityField(serializers.Field):
                 elif version:
                     apps_versions.max = apps_versions.get_default_maximum_appversion()
 
-            except AppVersion.DoesNotExist:
+            except AppVersion.DoesNotExist as exc:
                 raise exceptions.ValidationError(
                     gettext('Unknown max app version specified')
-                )
+                ) from exc
 
             try:
                 app_version_qs = app_version_qs.filter(~Q(version__contains='*'))
@@ -290,10 +294,10 @@ class VersionCompatibilityField(serializers.Field):
                     apps_versions.min_or_max_explicitly_set = True
                 elif version:
                     apps_versions.min = apps_versions.get_default_minimum_appversion()
-            except AppVersion.DoesNotExist:
+            except AppVersion.DoesNotExist as exc:
                 raise exceptions.ValidationError(
                     gettext('Unknown min app version specified')
-                )
+                ) from exc
 
             if existing_app and existing_app.locked_from_manifest:
                 if (

src/olympia/addons/serializers.py

@@ -500,7 +500,7 @@ class DeveloperVersionSerializer(VersionSerializer):
         try:
             self.parsed_data = parse_addon(value, addon=self.addon, user=request.user)
         except DuplicateAddonID as exc:
-            raise Conflict({self.field_name: exc.messages})
+            raise Conflict({self.field_name: exc.messages}) from exc
         return value
 
     def validate_is_disabled(self, disable):
@@ -562,13 +562,13 @@ class DeveloperVersionSerializer(VersionSerializer):
             try:
                 ReviewedSourceFileValidator()(data['source'], self.fields['source'])
             except exceptions.ValidationError as exc:
-                raise exceptions.ValidationError({'source': exc.detail})
+                raise exceptions.ValidationError({'source': exc.detail}) from exc
 
         if 'compatible_apps' in data:
             try:
                 self._post_validate_compatibility(data['compatible_apps'])
             except exceptions.ValidationError as exc:
-                raise exceptions.ValidationError({'compatibility': exc.detail})
+                raise exceptions.ValidationError({'compatibility': exc.detail}) from exc
 
         return data
 
@@ -793,7 +793,7 @@ class CurrentVersionSerializer(SimpleVersionSerializer):
             application = value[0]
             appversions = dict(zip(('min', 'max'), value[1:], strict=True))
         except ValueError as exc:
-            raise exceptions.ParseError(str(exc))
+            raise exceptions.ParseError(str(exc)) from exc
 
         version_qs = Version.objects.latest_public_compatible_with(
             application, appversions
@@ -928,8 +928,8 @@ class AddonPendingAuthorSerializer(AddonAuthorSerializer):
     def validate_user_id(self, value):
         try:
             user = UserProfile.objects.get(id=value)
-        except UserProfile.DoesNotExist:
-            raise exceptions.ValidationError(gettext('Account not found.'))
+        except UserProfile.DoesNotExist as exc:
+            raise exceptions.ValidationError(gettext('Account not found.')) from exc
 
         if not EmailUserRestriction.allow_email(
             user.email, restriction_type=RESTRICTION_TYPES.ADDON_SUBMISSION
@@ -950,13 +950,13 @@ class AddonPendingAuthorSerializer(AddonAuthorSerializer):
                 raise DjangoValidationError('')  # raise so we can catch below.
             for validator in user._meta.get_field('display_name').validators:
                 validator(user.display_name)
-        except DjangoValidationError:
+        except DjangoValidationError as exc:
             raise exceptions.ValidationError(
                 gettext(
                     'The account needs a display name before it can be added as an '
                     'author.'
                 )
-            )
+            ) from exc
 
         return value
 

src/olympia/addons/validators.py

@@ -20,7 +20,7 @@ class VerifyMozillaTrademark:
         try:
             verify_mozilla_trademark(value, user)
         except forms.ValidationError as exc:
-            raise exceptions.ValidationError(exc.message)
+            raise exceptions.ValidationError(exc.message) from exc
 
 
 class VersionLicenseValidator:
@@ -159,7 +159,7 @@ class VersionAddonMetadataValidator(AddonMetadataValidator):
                     'version: {missing_addon_metadata}.'
                 ).format(missing_addon_metadata=list(exc.detail)),
                 code='required',
-            )
+            ) from exc
 
 
 class AddonDefaultLocaleValidator:

src/olympia/addons/views.py

@@ -865,8 +865,8 @@ class AddonPendingAuthorViewSet(CreateModelMixin, AddonAuthorViewSet):
     def get_object_for_request(self, request):
         try:
             return self.get_queryset().get(user=request.user)
-        except AddonUserPendingConfirmation.DoesNotExist:
-            raise exceptions.PermissionDenied()
+        except AddonUserPendingConfirmation.DoesNotExist as exc:
+            raise exceptions.PermissionDenied() from exc
 
     def perform_create(self, serializer):
         instance = serializer.save()
@@ -995,8 +995,8 @@ class AddonFeaturedView(AddonSearchView):
     def get(self, request, *args, **kwargs):
         try:
             page_size = int(self.request.GET.get('page_size', api_settings.PAGE_SIZE))
-        except ValueError:
-            raise exceptions.ParseError('Invalid page_size parameter')
+        except ValueError as exc:
+            raise exceptions.ParseError('Invalid page_size parameter') from exc
 
         # Simulate pagination-like results, without actual pagination.
         queryset = self.filter_queryset(self.get_queryset()[:page_size])
@@ -1061,16 +1061,16 @@ class LanguageToolsView(ListAPIView):
             # app parameter is mandatory with appversion
             try:
                 application = AddonAppQueryParam(self.request.GET).get_value()
-            except ValueError:
+            except ValueError as exc:
                 raise exceptions.ParseError(
                     'Invalid or missing app parameter while appversion parameter is '
                     'set.'
-                )
+                ) from exc
             try:
                 value = AddonAppVersionQueryParam(self.request.GET).get_values()
                 appversions = {'min': value[1], 'max': value[2]}
-            except ValueError:
-                raise exceptions.ParseError('Invalid appversion parameter.')
+            except ValueError as exc:
+                raise exceptions.ParseError('Invalid appversion parameter.') from exc
         else:
             appversions = None
             application = None
@@ -1082,11 +1082,11 @@ class LanguageToolsView(ListAPIView):
         if AddonTypeQueryParam.query_param in self.request.GET or appversions:
             try:
                 addon_types = tuple(AddonTypeQueryParam(self.request.GET).get_values())
-            except ValueError:
+            except ValueError as exc:
                 raise exceptions.ParseError(
                     'Invalid or missing type parameter while appversion '
                     'parameter is set.'
-                )
+                ) from exc
         else:
             addon_types = (amo.ADDON_LPAPP, amo.ADDON_DICT)
 

src/olympia/amo/admin.py

@@ -118,8 +118,8 @@ class AMOModelAdminChangeList(ChangeList):
         else:
             try:
                 result_list = paginator.page(self.page_num).object_list
-            except InvalidPage:
-                raise IncorrectLookupParameters
+            except InvalidPage as exc:
+                raise IncorrectLookupParameters from exc
 
         self.result_count = result_count
         self.show_full_result_count = self.model_admin.show_full_result_count

src/olympia/amo/fields.py

@@ -56,7 +56,7 @@ class IPAddressBinaryField(VarBinaryField):
             # bytestring - i.e. what's stored in the db; or an IPv4Address|IPv6Address.
             return ipaddress.ip_address(value) if value is not None else None
         except Exception as exc:
-            raise exceptions.ValidationError(exc)
+            raise exceptions.ValidationError(exc) from exc
 
     def get_prep_value(self, value):
         return self.to_python(value).packed if value is not None else None
@@ -85,10 +85,10 @@ class ReCaptchaField(UpstreamReCaptchaField):
 def validate_cidr(value):
     try:
         ipaddress.ip_network(value)
-    except ValueError:
+    except ValueError as exc:
         raise exceptions.ValidationError(
             _('Enter a valid IP4 or IP6 network.'), code='invalid'
-        )
+        ) from exc
 
 
 class CIDRField(models.Field):
@@ -122,7 +122,7 @@ class CIDRField(models.Field):
         try:
             return ipaddress.ip_network(value)
         except Exception as exc:
-            raise exceptions.ValidationError(exc)
+            raise exceptions.ValidationError(exc) from exc
 
     def get_prep_lookup(self, lookup_type, value):
         if lookup_type == 'exact':

src/olympia/amo/management/commands/addnewversion.py

@@ -20,8 +20,8 @@ class Command(BaseCommand):
     def handle(self, *args, **options):
         try:
             do_addnewversion(options['application_name'], options['version'])
-        except IndexError:
-            raise CommandError(self.help)
+        except IndexError as exc:
+            raise CommandError(self.help) from exc
 
         msg = 'Adding version {!r} to application {!r}\n'.format(
             options['version'],
@@ -36,5 +36,5 @@ def do_addnewversion(application, version):
         raise CommandError('Application %r does not exist.' % application)
     try:
         AppVersion.objects.create(application=amo.APPS[application].id, version=version)
-    except IntegrityError as e:
-        raise CommandError(f'Version {version!r} already exists: {e!r}')
+    except IntegrityError as exc:
+        raise CommandError(f'Version {version!r} already exists: {exc!r}') from exc

src/olympia/amo/middleware.py

@@ -330,10 +330,10 @@ class SetRemoteAddrFromForwardedFor(MiddlewareMixin):
                     if not value:
                         raise IndexError
                     request.META['REMOTE_ADDR'] = value
-                except IndexError:
+                except IndexError as exc:
                     # Shouldn't happen, must be a misconfiguration, raise an error
                     # rather than potentially use/record incorrect IPs.
-                    raise ImproperlyConfigured('Invalid HTTP_X_FORWARDED_FOR')
+                    raise ImproperlyConfigured('Invalid HTTP_X_FORWARDED_FOR') from exc
 
 
 class RequestIdMiddleware(MiddlewareMixin):

src/olympia/amo/pagination.py

@@ -44,8 +44,8 @@ class ESPaginator(Paginator):
         """
         try:
             number = int(number)
-        except (TypeError, ValueError):
-            raise PageNotAnInteger('That page number is not an integer')
+        except (TypeError, ValueError) as exc:
+            raise PageNotAnInteger('That page number is not an integer') from exc
         if number < 1:
             raise EmptyPage('That page number is less than 1')
         return number

src/olympia/amo/sitemap.py

@@ -479,8 +479,8 @@ def get_sitemap_path(section, app, page=1):
             raise InvalidSection
         try:
             page = int(page)
-        except ValueError:
-            raise PageNotAnInteger
+        except ValueError as exc:
+            raise PageNotAnInteger from exc
         if app is None:
             # If we don't have a section or app, we don't need a complex directory
             # structure and we can call the first page 'sitemap' for convenience

src/olympia/amo/tests/__init__.py

@@ -1209,13 +1209,13 @@ def safe_exec(string, value=None, globals_=None, locals_=None):
     locals_ = locals_ or {}
     try:
         exec(force_str(string), globals_ or globals(), locals_)
-    except Exception as e:
+    except Exception as exc:
         if value:
             raise AssertionError(
-                f'Could not exec {string.strip()!r} (from value {value!r}): {e}'
-            )
+                f'Could not exec {string.strip()!r} (from value {value!r}): {exc}'
+            ) from exc
         else:
-            raise AssertionError(f'Could not exec {string.strip()!r}: {e}')
+            raise AssertionError(f'Could not exec {string.strip()!r}: {exc}') from exc
     return locals_
 
 

src/olympia/amo/views.py

@@ -245,11 +245,11 @@ def sitemap(request):
             )
             patch_cache_control(response, max_age=60 * 60)
 
-    except EmptyPage:
-        raise Http404('Page %s empty' % page)
-    except PageNotAnInteger:
-        raise Http404('No page "%s"' % page)
-    except InvalidSection:
-        raise Http404('No sitemap available for section: %r' % section)
+    except EmptyPage as exc:
+        raise Http404('Page %s empty' % page) from exc
+    except PageNotAnInteger as exc:
+        raise Http404('No page "%s"' % page) from exc
+    except InvalidSection as exc:
+        raise Http404('No sitemap available for section: %r' % section) from exc
 
     return response

src/olympia/api/authentication.py

@@ -113,7 +113,7 @@ class SessionIDAuthentication(BaseAuthentication):
 
         try:
             check_and_update_fxa_access_token(request)
-        except IdentificationError:
+        except IdentificationError as exc:
             log.info(
                 'User access token refresh failed; user needs to login to FxA again'
             )
@@ -123,7 +123,7 @@ class SessionIDAuthentication(BaseAuthentication):
                 ),
                 'code': 'ERROR_AUTHENTICATION_EXPIRED',
             }
-            raise exceptions.AuthenticationFailed(msg)
+            raise exceptions.AuthenticationFailed(msg) from exc
 
         # Set user in thread like UserAndAddrMiddleware does.
         core.set_user(user)
@@ -183,18 +183,18 @@ class JWTKeyAuthentication(BaseAuthentication):
                 )
                 # Re-raise to deal with them properly.
                 raise exc
-            except TypeError:
+            except TypeError as exc:
                 msg = gettext('Wrong type for one or more keys in payload')
-                raise exceptions.AuthenticationFailed(msg)
-            except jwt.ExpiredSignatureError:
+                raise exceptions.AuthenticationFailed(msg) from exc
+            except jwt.ExpiredSignatureError as exc:
                 msg = gettext('Signature has expired.')
-                raise exceptions.AuthenticationFailed(msg)
-            except jwt.DecodeError:
+                raise exceptions.AuthenticationFailed(msg) from exc
+            except jwt.DecodeError as exc:
                 msg = gettext('Error decoding signature.')
-                raise exceptions.AuthenticationFailed(msg)
-            except jwt.InvalidTokenError:
+                raise exceptions.AuthenticationFailed(msg) from exc
+            except jwt.InvalidTokenError as exc:
                 msg = gettext('Invalid JWT Token.')
-                raise exceptions.AuthenticationFailed(msg)
+                raise exceptions.AuthenticationFailed(msg) from exc
             # Note: AuthenticationFailed can also be raised directly from our
             # jwt_decode_handler.
 
@@ -220,9 +220,9 @@ class JWTKeyAuthentication(BaseAuthentication):
             raise exceptions.AuthenticationFailed(msg)
         try:
             api_key = APIKey.get_jwt_key(key=payload['iss'])
-        except APIKey.DoesNotExist:
+        except APIKey.DoesNotExist as exc:
             msg = 'Invalid API Key.'
-            raise exceptions.AuthenticationFailed(msg)
+            raise exceptions.AuthenticationFailed(msg) from exc
 
         if api_key.user.deleted:
             msg = 'User account is disabled.'
@@ -269,8 +269,12 @@ class UnsubscribeTokenAuthentication(BaseAuthentication):
                 request.data.get('token'), request.data.get('hash')
             )
             user = UserProfile.objects.get(email=email)
-        except ValueError:
-            raise exceptions.AuthenticationFailed(gettext('Invalid token or hash.'))
-        except UserProfile.DoesNotExist:
-            raise exceptions.AuthenticationFailed(gettext('Email address not found.'))
+        except ValueError as exc:
+            raise exceptions.AuthenticationFailed(
+                gettext('Invalid token or hash.')
+            ) from exc
+        except UserProfile.DoesNotExist as exc:
+            raise exceptions.AuthenticationFailed(
+                gettext('Email address not found.')
+            ) from exc
         return (user, None)

src/olympia/api/fields.py

@@ -374,11 +374,11 @@ class SlugOrPrimaryKeyRelatedField(serializers.RelatedField):
         except Exception:
             try:
                 return self.queryset.get(**{self.slug_field: data})
-            except ObjectDoesNotExist:
+            except ObjectDoesNotExist as exc:
                 msg = _('Invalid pk or slug "%s" - object does not exist.') % smart_str(
                     data
                 )
-                raise exceptions.ValidationError(msg)
+                raise exceptions.ValidationError(msg) from exc
 
 
 class OutgoingSerializerMixin:

src/olympia/api/jwt_auth.py

@@ -55,9 +55,11 @@ def jwt_decode_handler(token, get_api_key=APIKey.get_jwt_key):
 
     try:
         api_key = get_api_key(key=token_data['iss'])
-    except ObjectDoesNotExist:
+    except ObjectDoesNotExist as exc:
         log.info('No API key for JWT issuer: {}'.format(token_data['iss']))
-        raise exceptions.AuthenticationFailed(detail='Unknown JWT iss (issuer).')
+        raise exceptions.AuthenticationFailed(
+            detail='Unknown JWT iss (issuer).'
+        ) from exc
 
     # TODO: add nonce checking to prevent replays. bug 1213354.
 
@@ -94,7 +96,7 @@ def jwt_decode_handler(token, get_api_key=APIKey.get_jwt_key):
             'Missing required claim during JWT authentication: '
             '{e.__class__.__name__}: {e}'.format(e=exc)
         )
-        raise exceptions.AuthenticationFailed(detail=f'Invalid JWT: {exc}.')
+        raise exceptions.AuthenticationFailed(detail=f'Invalid JWT: {exc}.') from exc
     except (jwt.exceptions.ImmatureSignatureError, jwt.InvalidIssuedAtError) as exc:
         log.info(
             'Invalid iat during JWT authentication: '
@@ -103,7 +105,7 @@ def jwt_decode_handler(token, get_api_key=APIKey.get_jwt_key):
         raise exceptions.AuthenticationFailed(
             detail='JWT iat (issued at time) is invalid. Make sure your '
             'system clock is synchronized with something like TLSdate.'
-        )
+        ) from exc
     except Exception as exc:
         log.warning(
             'Unhandled exception during JWT authentication: '

src/olympia/api/permissions.py

@@ -300,8 +300,8 @@ class ByHttpMethod(BasePermission):
     def has_permission(self, request, view):
         try:
             perm = self.method_permissions[request.method.lower()]
-        except KeyError:
-            raise MethodNotAllowed(request.method)
+        except KeyError as exc:
+            raise MethodNotAllowed(request.method) from exc
         result = perm.has_permission(request, view)
         if not result and hasattr(perm, 'message'):
             self.message = perm.message
@@ -310,8 +310,8 @@ class ByHttpMethod(BasePermission):
     def has_object_permission(self, request, view, obj):
         try:
             perm = self.method_permissions[request.method.lower()]
-        except KeyError:
-            raise MethodNotAllowed(request.method)
+        except KeyError as exc:
+            raise MethodNotAllowed(request.method) from exc
         result = perm.has_object_permission(request, view, obj)
         if not result and hasattr(perm, 'message'):
             self.message = perm.message

src/olympia/api/validators.py

@@ -13,8 +13,8 @@ class OneOrMorePrintableCharacterAPIValidator(OneOrMorePrintableCharacterValidat
     def __call__(self, value):
         try:
             return super().__call__(value)
-        except DjangoValidationError:
-            raise exceptions.ValidationError(self.message)
+        except DjangoValidationError as exc:
+            raise exceptions.ValidationError(self.message) from exc
 
 
 class NoURLsValidator:
@@ -22,4 +22,4 @@ class NoURLsValidator:
         try:
             verify_no_urls(value)
         except DjangoValidationError as exc:
-            raise exceptions.ValidationError(exc.message)
+            raise exceptions.ValidationError(exc.message) from exc

src/olympia/devhub/feeds.py

@@ -22,8 +22,8 @@ class ActivityFeedRSS(Feed):
         try:
             rsskey = request.GET.get('privaterss')
             rsskey = uuid.UUID(rsskey)
-        except ValueError:
-            raise http.Http404
+        except ValueError as exc:
+            raise http.Http404 from exc
 
         key = get_object_or_404(RssKey, key=rsskey.hex)
         return key

src/olympia/devhub/forms.py

@@ -413,13 +413,13 @@ class AuthorWaitingConfirmationForm(AuthorForm):
                     raise forms.ValidationError('')  # Caught below.
                 for validator in name_validators:
                     validator(user.display_name)
-            except forms.ValidationError:
+            except forms.ValidationError as exc:
                 raise forms.ValidationError(
                     gettext(
                         'The account needs a display name before it can be added '
                         'as an author.'
                     )
-                )
+                ) from exc
         return user
 
 
@@ -738,8 +738,10 @@ class WithSourceMixin:
                     raise forms.ValidationError(
                         self.get_invalid_source_file_type_message()
                     )
-            except (zipfile.BadZipFile, tarfile.ReadError, OSError, EOFError):
-                raise forms.ValidationError(gettext('Invalid or broken archive.'))
+            except (zipfile.BadZipFile, tarfile.ReadError, OSError, EOFError) as exc:
+                raise forms.ValidationError(
+                    gettext('Invalid or broken archive.')
+                ) from exc
         return source
 
 

src/olympia/devhub/views.py

@@ -101,8 +101,8 @@ MDN_BASE = 'https://developer.mozilla.org/en-US/Add-ons'
 def get_fileupload_by_uuid_or_40x(value, *, user):
     try:
         UUID(value)
-    except ValueError:
-        raise http.Http404()
+    except ValueError as exc:
+        raise http.Http404() from exc
     upload = get_object_or_404(FileUpload, uuid=value)
     if upload.user != user:
         raise PermissionDenied
@@ -731,8 +731,8 @@ def json_file_validation(request, addon_id, addon, file_id):
     file = get_object_or_404(File, version__addon=addon, id=file_id)
     try:
         result = file.validation
-    except File.validation.RelatedObjectDoesNotExist:
-        raise http.Http404
+    except File.validation.RelatedObjectDoesNotExist as exc:
+        raise http.Http404 from exc
     return JsonResponse(
         {
             'validation': result.processed_validation,

src/olympia/files/utils.py

@@ -181,8 +181,10 @@ class ManifestJSONExtractor:
             self.data = json.loads(json_string)
             if not isinstance(self.data, dict):
                 raise TypeError()
-        except Exception:
-            raise InvalidManifest(gettext('Could not parse the manifest file.'))
+        except Exception as exc:
+            raise InvalidManifest(
+                gettext('Could not parse the manifest file.')
+            ) from exc
 
     def get(self, key, default=None):
         return self.data.get(key, default)
@@ -343,17 +345,17 @@ class ManifestJSONExtractor:
             qs = AppVersion.objects.filter(application=app.id)
             try:
                 min_appver = qs.get(version=strict_min_version)
-            except AppVersion.DoesNotExist:
+            except AppVersion.DoesNotExist as exc:
                 msg = gettext(
                     'Unknown "strict_min_version" {appver} for {app}'.format(
                         app=app.pretty, appver=strict_min_version
                     )
                 )
-                raise forms.ValidationError(msg)
+                raise forms.ValidationError(msg) from exc
 
             try:
                 max_appver = qs.get(version=strict_max_version)
-            except AppVersion.DoesNotExist:
+            except AppVersion.DoesNotExist as exc:
                 # If the specified strict_max_version can't be found, raise an
                 # error: we used to use '*' instead but this caused more
                 # problems, especially with langpacks that are really specific
@@ -363,7 +365,7 @@ class ManifestJSONExtractor:
                         app=app.pretty, appver=strict_max_version
                     )
                 )
-                raise forms.ValidationError(msg)
+                raise forms.ValidationError(msg) from exc
 
             if app == amo.ANDROID and self.gecko_android is not EMPTY_FALLBACK_DICT:
                 originated_from = amo.APPVERSIONS_ORIGINATED_FROM_MANIFEST_GECKO_ANDROID
@@ -389,11 +391,13 @@ class ManifestJSONExtractor:
             dictionaries = self.get('dictionaries', EMPTY_FALLBACK_DICT)
             key = force_str(list(dictionaries.keys())[0])
             return key[:255]
-        except (IndexError, UnicodeDecodeError):
+        except (IndexError, UnicodeDecodeError) as exc:
             # This shouldn't happen: the linter should prevent it, but
             # just in case, handle the error (without bothering with
             # translations as users should never see this).
-            raise forms.ValidationError('Invalid dictionaries object or langpack_id.')
+            raise forms.ValidationError(
+                'Invalid dictionaries object or langpack_id.'
+            ) from exc
 
     def parse(self, minimal=False):
         data = {
@@ -542,7 +546,7 @@ def archive_member_validator(member, ignore_filename_errors=False):
 
     try:
         force_str(filename)
-    except UnicodeDecodeError:
+    except UnicodeDecodeError as exc:
         # We can't log the filename unfortunately since it's encoding
         # is obviously broken :-/
         log.warning('Extraction error, invalid file name encoding')
@@ -550,7 +554,7 @@ def archive_member_validator(member, ignore_filename_errors=False):
             'Invalid file name in archive. Please make sure '
             'all filenames are utf-8 or latin1 encoded.'
         )
-        raise InvalidArchiveFile(msg)
+        raise InvalidArchiveFile(msg) from exc
 
     if not ignore_filename_errors:
         if (
@@ -733,17 +737,22 @@ def extract_extension_to_dest(source, dest=None, force_fsync=False):
                 archive.extractall(target)
         else:
             raise FileNotFoundError  # Unsupported file, shouldn't be reached
-    except (zipfile.BadZipFile, tarfile.ReadError, OSError, forms.ValidationError) as e:
+    except (
+        zipfile.BadZipFile,
+        tarfile.ReadError,
+        OSError,
+        forms.ValidationError,
+    ) as exc:
         if tempdir is not None:
             rm_local_tmp_dir(tempdir)
-        if isinstance(e, (FileNotFoundError, forms.ValidationError)):
+        if isinstance(exc, (FileNotFoundError, forms.ValidationError)):
             # We let FileNotFoundError (which are a subclass of IOError, or
             # rather OSError but that's an alias) and ValidationError be
             # raised, the caller will have to deal with it.
             raise
         # Any other exceptions we caught, we raise a generic ValidationError
         # instead.
-        raise forms.ValidationError(gettext('Invalid or broken archive.'))
+        raise forms.ValidationError(gettext('Invalid or broken archive.')) from exc
     return target
 
 
@@ -844,14 +853,16 @@ def parse_xpi(
 
     except forms.ValidationError:
         raise
-    except zipfile.BadZipFile:
-        raise forms.ValidationError(gettext('Invalid or corrupted file.'))
-    except Exception as exception:
+    except zipfile.BadZipFile as exc:
+        raise forms.ValidationError(gettext('Invalid or corrupted file.')) from exc
+    except Exception as exc:
         # We don't really know what happened, so even though we return a
         # generic message about the manifest, don't raise InvalidManifest: it's
         # not just invalid, it's worse... We want the validation to stop there.
-        log.exception(f'XPI parse error ({exception.__class__})')
-        raise forms.ValidationError(gettext('Could not parse the manifest file.'))
+        log.exception(f'XPI parse error ({exc.__class__})')
+        raise forms.ValidationError(
+            gettext('Could not parse the manifest file.')
+        ) from exc
 
     if minimal:
         return xpi_info
@@ -1078,8 +1089,8 @@ def write_crx_as_xpi(chunks, target):
                 start_position = 12 + header_length
             else:
                 raise InvalidOrUnsupportedCrx('Unsupported CRX version')
-        except struct.error:
-            raise InvalidOrUnsupportedCrx('Invalid or corrupt CRX file')
+        except struct.error as exc:
+            raise InvalidOrUnsupportedCrx('Invalid or corrupt CRX file') from exc
 
         # We can start reading the zip to write it where it needs to live on
         # the filesystem and then return the hash to the caller. If we somehow

src/olympia/git/utils.py

@@ -255,10 +255,10 @@ class AddonGitRepository:
             try:
                 master_ref = 'refs/heads/master'
                 git_repository.lookup_reference(master_ref)
-            except KeyError:
+            except KeyError as exc:
                 message = f'Reference "{master_ref}" not found'
                 log.exception(message)
-                raise MissingMasterBranchError(message)
+                raise MissingMasterBranchError(message) from exc
 
         return git_repository
 
@@ -393,10 +393,10 @@ class AddonGitRepository:
         """Lookup or create the branch named `name`"""
         try:
             branch = self.git_repository.branches.get(name)
-        except pygit2.GitError:
+        except pygit2.GitError as exc:
             message = f'Reference for branch "{name}" is broken'
             log.exception(message)
-            raise BrokenRefError(message)
+            raise BrokenRefError(message) from exc
 
         if branch is None:
             branch = self.git_repository.create_branch(

src/olympia/ratings/utils.py

@@ -10,8 +10,10 @@ def get_grouped_ratings(request, addon):
             show_grouped_ratings = serializers.BooleanField().to_internal_value(
                 request.GET['show_grouped_ratings']
             )
-        except serializers.ValidationError:
-            raise ParseError('show_grouped_ratings parameter should be a boolean')
+        except serializers.ValidationError as exc:
+            raise ParseError(
+                'show_grouped_ratings parameter should be a boolean'
+            ) from exc
         if show_grouped_ratings and addon:
             try:
                 aggregate = addon.ratingaggregate

src/olympia/ratings/views.py

@@ -199,11 +199,11 @@ class RatingViewSet(AddonChildMixin, ModelViewSet):
                     )
                     if show_flags_for != request.user.pk:
                         raise serializers.ValidationError
-                except serializers.ValidationError:
+                except serializers.ValidationError as exc:
                     raise ParseError(
                         'show_flags_for parameter value should be equal to '
                         'the user id of the authenticated user'
-                    )
+                    ) from exc
         return self._should_include_flags
 
     def check_permissions(self, request):
@@ -242,14 +242,14 @@ class RatingViewSet(AddonChildMixin, ModelViewSet):
             if user_identifier:
                 try:
                     user_identifier = int(user_identifier)
-                except ValueError:
-                    raise ParseError('user parameter should be an integer.')
+                except ValueError as exc:
+                    raise ParseError('user parameter should be an integer.') from exc
                 qs = qs.filter(user=user_identifier)
             if version_identifier:
                 try:
                     version_identifier = int(version_identifier)
-                except ValueError:
-                    raise ParseError('version parameter should be an integer.')
+                except ValueError as exc:
+                    raise ParseError('version parameter should be an integer.') from exc
                 qs = qs.filter(version=version_identifier)
             elif addon_identifier:
                 # When filtering on addon but not on version, only return the
@@ -270,23 +270,23 @@ class RatingViewSet(AddonChildMixin, ModelViewSet):
             if score_filter:
                 try:
                     scores = [int(score) for score in score_filter.split(',')]
-                except ValueError:
+                except ValueError as exc:
                     raise ParseError(
                         'score parameter should be an integer or a list of '
                         'integers (separated by a comma).'
-                    )
+                    ) from exc
                 qs = qs.filter(rating__in=scores)
             if exclude_ratings:
                 try:
                     exclude_ratings = [
                         int(rating) for rating in exclude_ratings.split(',')
                     ]
-                except ValueError:
+                except ValueError as exc:
                     raise ParseError(
                         'exclude_ratings parameter should be an '
                         'integer or a list of integers '
                         '(separated by a comma).'
-                    )
+                    ) from exc
                 qs = qs.exclude(pk__in=exclude_ratings)
 
         if not addon_identifier:
@@ -316,11 +316,11 @@ class RatingViewSet(AddonChildMixin, ModelViewSet):
                 )
                 if show_permissions_for != request.user.pk:
                     raise serializers.ValidationError
-            except serializers.ValidationError:
+            except serializers.ValidationError as exc:
                 raise ParseError(
                     'show_permissions_for parameter value should be equal to '
                     'the user id of the authenticated user'
-                )
+                ) from exc
             extra_data['can_reply'] = self.check_can_reply_permission_for_ratings_list()
         # Call this here so the validation checks on the `show_flags_for` are
         # carried out even when there are no results to serialize.

src/olympia/reviewers/models.py

@@ -472,8 +472,8 @@ class AutoApprovalSummary(ModelBase):
             old_version = self.find_previous_confirmed_version()
             old_size = find_code_size(old_version) if old_version else 0
             new_size = find_code_size(self.version)
-        except FileValidation.DoesNotExist:
-            raise AutoApprovalNoValidationResultError()
+        except FileValidation.DoesNotExist as exc:
+            raise AutoApprovalNoValidationResultError() from exc
         # We don't really care about whether it's a negative or positive change
         # in size, we just need the absolute value (if there is no current
         # public version, that value ends up being the total code size of the
@@ -520,8 +520,8 @@ class AutoApprovalSummary(ModelBase):
     def _count_linter_flag(cls, version, flag):
         try:
             validation = version.file.validation
-        except FileValidation.DoesNotExist:
-            raise AutoApprovalNoValidationResultError()
+        except FileValidation.DoesNotExist as exc:
+            raise AutoApprovalNoValidationResultError() from exc
         validation_data = json.loads(validation.validation)
         return sum(
             flag in message['id'] for message in validation_data.get('messages', [])
@@ -531,8 +531,8 @@ class AutoApprovalSummary(ModelBase):
     def _count_metadata_property(cls, version, prop):
         try:
             validation = version.file.validation
-        except FileValidation.DoesNotExist:
-            raise AutoApprovalNoValidationResultError()
+        except FileValidation.DoesNotExist as exc:
+            raise AutoApprovalNoValidationResultError() from exc
         validation_data = json.loads(validation.validation)
         return len(validation_data.get('metadata', {}).get(prop, []))
 

src/olympia/reviewers/serializers.py

@@ -90,8 +90,10 @@ class FileEntriesMixin:
         # Caching the commit to avoid calling revparse_single many times.
         try:
             return self.git_repo.revparse_single(self._get_version().git_hash)
-        except pygit2.InvalidSpecError:
-            raise NotFound("Couldn't find the requested version in git-repository")
+        except pygit2.InvalidSpecError as exc:
+            raise NotFound(
+                "Couldn't find the requested version in git-repository"
+            ) from exc
 
     @cached_property
     def tree(self):

src/olympia/reviewers/views.py

@@ -1019,8 +1019,8 @@ def download_git_stored_file(request, version_id, filename):
 
     try:
         addon = version.addon
-    except Addon.DoesNotExist:
-        raise http.Http404
+    except Addon.DoesNotExist as exc:
+        raise http.Http404 from exc
 
     if version.channel == amo.CHANNEL_LISTED:
         is_owner = acl.check_addon_ownership(request.user, addon, allow_developer=True)
@@ -1045,8 +1045,8 @@ def download_git_stored_file(request, version_id, filename):
         if blob_or_tree.type == pygit2.GIT_OBJ_TREE:
             return http.HttpResponseBadRequest("Can't serve directories")
         selected_file = serializer._get_entries()[filename]
-    except (KeyError, NotFound):
-        raise http.Http404()
+    except (KeyError, NotFound) as exc:
+        raise http.Http404() from exc
 
     actual_blob = serializer.git_repo[blob_or_tree.oid]
 
@@ -1225,8 +1225,8 @@ class AddonReviewerViewSet(GenericViewSet):
             raise PermissionDenied
         try:
             result = file.validation
-        except File.validation.RelatedObjectDoesNotExist:
-            raise http.Http404
+        except File.validation.RelatedObjectDoesNotExist as exc:
+            raise http.Http404 from exc
         return JsonResponse(
             {
                 'validation': result.processed_validation,

src/olympia/scanners/models.py

@@ -195,11 +195,11 @@ class AbstractScannerRule(ModelBase):
                     'definition': _('The definition is not valid: %(error)s')
                     % {'error': syntaxError}
                 }
-            )
-        except Exception:
+            ) from syntaxError
+        except Exception as exc:
             raise ValidationError(
                 {'definition': _('An error occurred when compiling the definition')}
-            )
+            ) from exc
 
 
 class ScannerRule(AbstractScannerRule):

src/olympia/scanners/tasks.py

@@ -122,9 +122,9 @@ def _run_scanner_for_url(scanner_result, url, scanner, api_url, api_key):
 
     try:
         data = response.json()
-    except ValueError:
+    except ValueError as exc:
         # Log the response body when JSON decoding has failed.
-        raise ValueError(response.text)
+        raise ValueError(response.text) from exc
 
     if response.status_code != 200 or 'error' in data:
         raise ValueError(data)
@@ -446,9 +446,9 @@ def call_mad_api(all_results, upload_pk):
 
         try:
             data = response.json()
-        except ValueError:
+        except ValueError as exc:
             # Log the response body when JSON decoding has failed.
-            raise ValueError(response.text)
+            raise ValueError(response.text) from exc
 
         if response.status_code != 200:
             raise ValueError(data)

src/olympia/search/filters.py

@@ -265,10 +265,10 @@ class AddonGuidQueryParam(AddonQueryMultiParam):
                 value = force_str(urlsafe_base64_decode(force_str(value[4:])))
                 if not amo.ADDON_GUID_PATTERN.match(value):
                     raise ValueError()
-            except (TypeError, ValueError):
+            except (TypeError, ValueError) as exc:
                 raise ValueError(
                     gettext('Invalid Return To AMO guid (not in base64url format?)')
-                )
+                ) from exc
             # Filter on the now decoded guid param as normal...
             filters = super().get_es_query([value])
             # If the switch to enable all listed add-ons for RTAMO is on, we
@@ -310,7 +310,7 @@ class AddonCategoryQueryParam(AddonQueryParam):
         try:
             types = AddonTypeQueryParam(self.query_data).get_values()
             self.reverse_dict = [CATEGORIES[type_] for type_ in types]
-        except KeyError:
+        except KeyError as exc:
             raise ValueError(
                 gettext(
                     'Invalid combination of "%s" and "%s" parameters.'
@@ -319,7 +319,7 @@ class AddonCategoryQueryParam(AddonQueryParam):
                         self.query_param,
                     )
                 )
-            )
+            ) from exc
 
     def get_value(self):
         value = super().get_value()
@@ -938,7 +938,7 @@ class SearchParameterFilter(BaseFilterBackend):
                 if param_class.query_param in request.GET:
                     clauses.extend(param_class(request.GET).get_es_query())
             except ValueError as exc:
-                raise serializers.ValidationError(*exc.args)
+                raise serializers.ValidationError(*exc.args) from exc
         return clauses
 
     def filter_queryset(self, request, qs, view):
@@ -1061,8 +1061,8 @@ class SortingFilter(BaseFilterBackend):
 
         try:
             order_by = [self.SORTING_PARAMS[name] for name in split_sort_params]
-        except KeyError:
-            raise serializers.ValidationError('Invalid "sort" parameter.')
+        except KeyError as exc:
+            raise serializers.ValidationError('Invalid "sort" parameter.') from exc
 
         return qs.sort(*order_by)
 

src/olympia/users/admin.py

@@ -267,8 +267,8 @@ class UserAdmin(AMOModelAdmin):
             try:
                 if lookup_field == 'email':
                     user = UserProfile.objects.get(email=object_id)
-            except UserProfile.DoesNotExist:
-                raise http.Http404
+            except UserProfile.DoesNotExist as exc:
+                raise http.Http404 from exc
             url = request.path.replace(object_id, str(user.id), 1)
             if request.GET:
                 url += '?' + request.GET.urlencode()

src/olympia/users/management/commands/activate_user.py

@@ -26,8 +26,8 @@ class Command(BaseCommand):
 
         try:
             profile = UserProfile.objects.get(email=email)
-        except UserProfile.DoesNotExist:
-            raise CommandError('User with email %s not found' % email)
+        except UserProfile.DoesNotExist as exc:
+            raise CommandError('User with email %s not found' % email) from exc
 
         admin_msg = ''
         if set_admin:

src/olympia/users/management/commands/createsuperuser.py

@@ -73,7 +73,7 @@ and email address and that's it.
                             'You must use --%s with --noinput.' % field_name
                         )
             except exceptions.ValidationError as exc:
-                raise CommandError('; '.join(exc.messages))
+                raise CommandError('; '.join(exc.messages)) from exc
         else:
             user_data = {
                 field_name: self.get_value(field_name)

src/olympia/users/utils.py

@@ -37,9 +37,9 @@ class UnsubscribeCode:
         try:
             decoded = base64.urlsafe_b64decode(force_bytes(code))
             email = decoded
-        except (ValueError, TypeError):
+        except (ValueError, TypeError) as exc:
             # Data is broken
-            raise ValueError
+            raise ValueError from exc
 
         if cls.make_secret(decoded) != hash:
             log.info('[Tampering] Unsubscribe link data does not match hash')

src/olympia/zadmin/management/commands/addusertogroup.py

@@ -38,9 +38,9 @@ def do_adduser(user, group):
 
         GroupUser.objects.create(user=user, group=group)
 
-    except IntegrityError as e:
-        raise CommandError('User is already in that group? %s' % e)
-    except UserProfile.DoesNotExist:
-        raise CommandError(f'User ({user}) does not exist.')
-    except Group.DoesNotExist:
-        raise CommandError(f'Group ({group}) does not exist.')
+    except IntegrityError as exc:
+        raise CommandError('User is already in that group? %s' % exc) from exc
+    except UserProfile.DoesNotExist as exc:
+        raise CommandError(f'User ({user}) does not exist.') from exc
+    except Group.DoesNotExist as exc:
+        raise CommandError(f'Group ({group}) does not exist.') from exc

src/olympia/zadmin/management/commands/removeuserfromgroup.py

@@ -37,7 +37,7 @@ def do_removeuser(user, group):
 
         # Doesn't actually check if the user was in the group or not.
         GroupUser.objects.filter(user=user, group=group).delete()
-    except UserProfile.DoesNotExist:
-        raise CommandError(f'User ({user}) does not exist.')
-    except Group.DoesNotExist:
-        raise CommandError(f'Group ({group}) does not exist.')
+    except UserProfile.DoesNotExist as exc:
+        raise CommandError(f'User ({user}) does not exist.') from exc
+    except Group.DoesNotExist as exc:
+        raise CommandError(f'Group ({group}) does not exist.') from exc