Don't crash on an UnexpectedSituation (#2453)

Rather than crash and prematurely end an invocation with potentially
more bugs left to process, gracefully handle `UnexpectedSituation`
exceptions and continue processing the rest of the bugs.

Necessary because there are still some Git-sourced CVEs in Datastore
that require reimporting from GCS, and tickle this edge case.

tools/datafix/reimport_gcs_record.py

@@ -171,7 +171,12 @@ def main() -> None:
   try:
     with ds_client.transaction() as xact:
       for bug in result_to_fix:
-        bug_in_gcs = objname_for_bug(ds_client, bug)
+        try:
+          bug_in_gcs = objname_for_bug(ds_client, bug)
+        except UnexpectedSituation as e:
+          if args.verbose:
+            print(f"Skipping {bug['db_id']}, got {e}\n")
+          continue
         if args.verbose:
           print(f"Resetting creation time for {bug_in_gcs['uri']}")
         if not args.dryrun: