fix: Fail gracefully if could not import rpc_status module

Author: NickGoog

google/api_core/exceptions.py

@@ -28,16 +28,21 @@
 
 from google.rpc import error_details_pb2
 
+
+def _warn_could_not_import_grpcio_status():
+    warnings.warn(
+        "Please install grpcio-status to obtain helpful grpc error messages.",
+        ImportWarning,
+    )
+
+
 try:
     import grpc
 
     try:
         from grpc_status import rpc_status
     except ImportError:  # pragma: NO COVER
-        warnings.warn(
-            "Please install grpcio-status to obtain helpful grpc error messages.",
-            ImportWarning,
-        )
+        _warn_could_not_import_grpcio_status()
         rpc_status = None
 except ImportError:  # pragma: NO COVER
     grpc = None
@@ -560,6 +565,11 @@ def _is_informative_grpc_error(rpc_exc):
 
 
 def _parse_grpc_error_details(rpc_exc):
+    # pragma: NO COVER
+    if not rpc_status:
+        _warn_could_not_import_grpcio_status()
+        return [], None
+    # pragma: NO COVER
     try:
         status = rpc_status.from_call(rpc_exc)
     except NotImplementedError:  # workaround

tests/unit/test_exceptions.py

@@ -393,3 +393,24 @@ def test_error_details_from_grpc_response_unknown_error():
         and exception.domain is None
         and exception.metadata is None
     )
+
+
+@pytest.mark.skipif(grpc is None, reason="gRPC not importable")
+def test_from_grpc_error_warns_if_not_grpc():
+    try:
+        from grpc_status import rpc_status
+        del rpc_status  # Unused.
+        # Warning won't trigger.
+        return
+    except ImportError:  # pragma: NO COVER
+        # Proceed to rest of test.
+        pass
+
+    error = mock.create_autospec(grpc.Call, instance=True)
+
+    with mock.patch("warnings.warn", autospec=True) as mock_warn:
+        exceptions.from_grpc_error(error)
+        mock_warn.assert_called_with(
+            "Please install grpcio-status to obtain helpful grpc error messages.",
+            ImportWarning,
+        )