Update errors to extend BaseRepoError

In order to better analyze and track repo errors, repo command failures
need to be tied to specific errors in repo source code.

Additionally a new GitCommandError was added to differentiate between
general git related errors to failed git commands. Git commands that opt
into verification will raise a GitCommandError if the command failed.

The first step in this process is a general error refactoring

Bug: b/293344017
Change-Id: I46944b1825ce892757c8dd3f7e2fab7e460760c0
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/380994
Commit-Queue: Jason Chang <jasonnc@google.com>
Reviewed-by: Aravind Vasudevan <aravindvasudev@google.com>
Tested-by: Jason Chang <jasonnc@google.com>
Reviewed-by: Joanna Wang <jojwang@google.com>

tests/test_error.py

@@ -19,6 +19,15 @@ import pickle
 import unittest
 
 import error
+import project
+import git_command
+from subcmds import all_modules
+
+imports = all_modules + [
+    error,
+    project,
+    git_command,
+]
 
 
 class PickleTests(unittest.TestCase):
@@ -26,10 +35,11 @@ class PickleTests(unittest.TestCase):
 
     def getExceptions(self):
         """Return all our custom exceptions."""
-        for name in dir(error):
-            cls = getattr(error, name)
-            if isinstance(cls, type) and issubclass(cls, Exception):
-                yield cls
+        for entry in imports:
+            for name in dir(entry):
+                cls = getattr(entry, name)
+                if isinstance(cls, type) and issubclass(cls, Exception):
+                    yield cls
 
     def testExceptionLookup(self):
         """Make sure our introspection logic works."""