Bug 1636251: report |./mach| errors with Sentry r=rstewart

These errors are reported to the "mach" project here:
https://sentry.prod.mozaws.net/operations/mach/

Should only report exceptions caused by a failure in `mach` or its subcommands. Build/test/etc failures
should not be sent to Sentry.

Differential Revision: https://phabricator.services.mozilla.com/D74738

python/mach/mach/main.py

@@ -18,6 +18,7 @@ import traceback
 import uuid
 from collections import Iterable
 
+from mach.sentry import register_sentry, report_exception
 from six import string_types
 
 from .base import (
@@ -319,6 +320,7 @@ To see more help for a specific command, run:
         Returns the integer exit code that should be used. 0 means success. All
         other values indicate failure.
         """
+        register_sentry()
 
         # If no encoding is defined, we default to UTF-8 because without this
         # Python 2.7 will assume the default encoding of ASCII. This will blow
@@ -375,6 +377,7 @@ To see more help for a specific command, run:
             stack = traceback.extract_tb(exc_tb)
 
             self._print_exception(sys.stdout, exc_type, exc_value, stack)
+            report_exception(exc_value)
 
             return 1
 
@@ -480,6 +483,7 @@ To see more help for a specific command, run:
             return e.exit_code
         except Exception:
             exc_type, exc_value, exc_tb = sys.exc_info()
+            report_exception(exc_value)
 
             # The first two frames are us and are never used.
             stack = traceback.extract_tb(exc_tb)[2:]

python/mach/mach/sentry.py

@@ -0,0 +1,59 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+from __future__ import absolute_import
+
+import os
+import re
+
+import sentry_sdk
+from six.moves.configparser import SafeConfigParser, NoOptionError
+
+from mozboot.util import get_state_dir
+
+
+# https://sentry.prod.mozaws.net/operations/mach/
+_SENTRY_DSN = "https://8228c9aff64949c2ba4a2154dc515f55@sentry.prod.mozaws.net/525"
+
+
+def register_sentry():
+    cfg_file = os.path.join(get_state_dir(), 'machrc')
+    config = SafeConfigParser()
+
+    if not config.read(cfg_file):
+        return
+
+    try:
+        telemetry_enabled = config.getboolean("build", "telemetry")
+    except NoOptionError:
+        return
+
+    if not telemetry_enabled:
+        return
+
+    sentry_sdk.init(_SENTRY_DSN, before_send=_settle_mach_module_id)
+
+
+def _settle_mach_module_id(sentry_event, exception):
+    # Sentry groups issues according to the stack frames and their associated
+    # "module" properties. However, one of the modules is being reported
+    # like "mach.commands.26a828ef5164403eaff4305ab4cb0fab" (with a generated id).
+    # This function replaces that generated id with the static string "<generated>"
+    # so that grouping behaves as expected
+
+    stacktrace_frames = sentry_event["exception"]["values"][0]["stacktrace"]["frames"]
+    for frame in stacktrace_frames:
+        module = frame.get("module")
+        if not module:
+            continue
+
+        module = re.sub("mach\\.commands\\.[a-f0-9]{32}", "mach.commands.<generated>",
+                        module)
+        frame["module"] = module
+    return sentry_event
+
+
+def report_exception(exception):
+    # sentry_sdk won't report the exception if `sentry-sdk.init(...)` hasn't been called
+    sentry_sdk.capture_exception(exception)