Incompatibility With Recent GCP SDK Versions

Describe your environment.

The code is an asynchronous workload running in GKE.

Python 3.7.9

google-api-core==1.22.3 google-auth==1.22.0 google-cloud-bigquery==1.20.0 google-cloud-core==1.3.0 google-cloud-error-reporting==0.32.1 google-cloud-kms==2.2.0 opencensus-context==0.1.1 opencensus-ext-google-cloud-clientlibs==0.1.2 opencensus-ext-grpc==0.7.1

Steps to reproduce.

1. Enable the google_cloud_clientlibs integration
2. Call the GCP KMS API using the Python SDK client.

What is the expected behavior?

The GRPC call to the KMS API is traced automatically.

What is the actual behavior?

The following (partially redacted) exception is raised because it seems that the opencensus.ext.grpc.utils. add_message_event function assumes that all Message objects will have ByteSize method. Recently the official GCP SDK packages for Python have begun to use the proto plus package, and that version of the Message object does not have the ByteSize method.

Additional context.

Traceback (most recent call last):
  File "/redacted.py", line 167, in redacted
    public_key = client.get_public_key(request={"name": key_name})
  File "/usr/local/lib/python3.7/site-packages/google/cloud/kms_v1/services/key_management_service/client.py", line 1026, in get_public_key
    response = rpc(request, retry=retry, timeout=timeout, metadata=metadata,)
  File "/usr/local/lib/python3.7/site-packages/google/api_core/gapic_v1/method.py", line 145, in __call__
    return wrapped_func(*args, **kwargs)
  File "/usr/local/lib/python3.7/site-packages/google/api_core/retry.py", line 286, in retry_wrapped_func
    on_error=on_error,
  File "/usr/local/lib/python3.7/site-packages/google/api_core/retry.py", line 184, in retry_target
    return target()
  File "/usr/local/lib/python3.7/site-packages/google/api_core/grpc_helpers.py", line 57, in error_remapped_callable
    return callable_(*args, **kwargs)
  File "/usr/local/lib/python3.7/site-packages/grpc/_interceptor.py", line 221, in __call__
    compression=compression)
  File "/usr/local/lib/python3.7/site-packages/grpc/_interceptor.py", line 256, in _with_call
    request)
  File "/usr/local/lib/python3.7/site-packages/opencensus/ext/grpc/client_interceptor.py", line 166, in intercept_unary_unary
    next(new_request))
  File "/usr/local/lib/python3.7/site-packages/opencensus/ext/grpc/utils.py", line 33, in wrap_iter_with_message_events
    message_id=message_id)
  File "/usr/local/lib/python3.7/site-packages/opencensus/ext/grpc/utils.py", line 18, in add_message_event
    uncompressed_size_bytes=proto_message.ByteSize()
  File "/usr/local/lib/python3.7/site-packages/proto/message.py", line 525, in __getattr__
    raise AttributeError(str(ex))
AttributeError: 'ByteSize'

[seandstewart]

proto-plus provides access to the underlying protobuf with the pb() classmethod.

https://proto-plus-python.readthedocs.io/en/stable/reference/message.html#proto.message.Message.pb

[aabmass]

No workaround, but the fix should be straightforward