Raise exception with helpful error on Client pickle.
Based on the discussion in #3191, raise an exception with a helpful error stating that Client classes are not pickleable.
Note to self: We probably want this in GAX also.
Raise exception with helpful error on Client pickle.
Based on the discussion in #3191, raise an exception with a helpful error stating that Client classes are not pickleable.
Note to self: We probably want this in GAX also.