Fix Pylint exception chaining warnings (#1519)

python/ccf/ledger.py

@@ -228,8 +228,8 @@ class Transaction:
             self._complete_read()
             self._read_header()
             return self
-        except:
-            raise StopIteration()
+        except Exception as e:
+            raise StopIteration() from e
 
 
 class Ledger:
@@ -275,7 +275,7 @@ class Ledger:
                 self._current_tx = Transaction(self._filenames[self._fileindex])
                 return next(self._current_tx)
             else:
-                raise StopIteration()
+                raise
 
     def __iter__(self):
         return self

tests/e2e_batched.py

@@ -127,7 +127,9 @@ def run_to_destruction(args):
                     break
 
             if time.time() > end_time:
-                raise TimeoutError(f"Node took longer than {timeout}s to terminate")
+                raise TimeoutError(
+                    f"Node took longer than {timeout}s to terminate"
+                ) from e
 
             network.ignore_errors_on_shutdown()
 

tests/e2e_suite.py

@@ -32,8 +32,8 @@ def run(args):
     for choice in args.test_suite:
         try:
             chosen_suite.extend(s.suites[choice])
-        except KeyError:
-            raise ValueError(f"Unhandled choice: {choice}")
+        except KeyError as e:
+            raise ValueError(f"Unhandled choice: {choice}") from e
 
     seed = None
     if os.getenv("SHUFFLE_SUITE"):

tests/infra/network.py

@@ -432,7 +432,7 @@ class Network:
                     else infra.node.NodeStatus.TRUSTED
                 ),
             )
-        except TimeoutError:
+        except TimeoutError as e:
             # The node can be safely discarded since it has not been
             # attributed a unique node_id by CCF
             LOG.error(f"New pending node {new_node.node_id} failed to join the network")
@@ -442,7 +442,7 @@ class Network:
                 # Throw accurate exceptions if known errors found in
                 for error in errors:
                     if "CODE_ID_NOT_FOUND" in error:
-                        raise CodeIdNotFound
+                        raise CodeIdNotFound from e
             raise
 
         return new_node

tests/infra/node.py

@@ -244,8 +244,8 @@ class Node:
                 assert (
                     rep.status_code == 200
                 ), f"An error occured after node {self.node_id} joined the network: {rep.body}"
-        except ccf.clients.CCFConnectionException:
-            raise TimeoutError(f"Node {self.node_id} failed to join the network")
+        except ccf.clients.CCFConnectionException as e:
+            raise TimeoutError(f"Node {self.node_id} failed to join the network") from e
 
     def get_ledger(self):
         return self.remote.get_ledger()

tests/suite/test_requirements.py

@@ -38,7 +38,7 @@ def ensure_reqs(check_reqs):
                 except Exception as e:
                     raise TestRequirementsNotMet(
                         f"Could not check if test requirements were met: {e}"
-                    )
+                    ) from e
 
             return func(network, args, *nargs, **kwargs)