Added TODO + fixed system test

Author: gkevinzheng

google/cloud/bigtable/data/exceptions.py

@@ -141,6 +141,8 @@ def __repr__(self):
         return f"{self.__class__.__name__}({message!r}, {self.exceptions!r})"
 
 
+# TODO: When working on mutations batcher, rework exception handling to guarantee that
+# MutationsExceptionGroup only stores FailedMutationEntryErrors. 
 class MutationsExceptionGroup(_BigtableExceptionGroup):
     """
     Represents one or more exceptions that occur during a bulk mutation operation

tests/system/v2_client/test_data_api.py

@@ -358,7 +358,7 @@ def test_table_mutate_rows_retries_timeout(data_table, rows_to_delete):
 
         statuses = data_table.mutate_rows([row, row_2])
         assert statuses[0].code == Code.OK
-        assert statuses[1].code == Code.INTERNAL
+        assert statuses[1].code == Code.DEADLINE_EXCEEDED
 
     # Retries with deadline 0 should do nothing.
     with mock.patch.object(