Bug 1878021 - Print the messages for `InvalidRepoPath` and `MissingVCSTool` when `_get_repository_object` encounters those exceptions r=firefox-build-system-reviewers,glandium

This should make it easier for a user to troubleshoot the problem,
instead of trying to decipher a subsequent exception from a function
call being attempted on the `None` returned by this function.

Differential Revision: https://phabricator.services.mozilla.com/D200496

python/mach/mach/sentry.py

@@ -4,6 +4,7 @@
 
 import abc
 import re
+import sys
 from pathlib import Path
 from threading import Thread
 
@@ -187,7 +188,8 @@ def _delete_server_name(sentry_event, _):
 def _get_repository_object(topsrcdir: Path):
     try:
         return get_repository_object(str(topsrcdir))
-    except (InvalidRepoPath, MissingVCSTool):
+    except (InvalidRepoPath, MissingVCSTool) as e:
+        print(f"Warning: {e}", file=sys.stderr)
         return None