Suppress stack trace for GitPushError

Change-Id: Idcd1cfb41cf1cf9a3bfb252f6a8c109cbce5a5f8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/7132480
Reviewed-by: Gavin Mak <gavinmak@google.com>
Commit-Queue: Josiah Kiehl <kiehl@google.com>

git_cl.py

@@ -7534,6 +7534,8 @@ def main(argv):
         DieWithError((
             'App Engine is misbehaving and returned HTTP %d, again. Keep faith '
             'and retry or visit go/isgaeup.\n%s') % (e.code, str(e)))
+    except GitPushError as e:
+        DieWithError(str(e))
     return 0