Merge pull request #7091 from kpayson64/python_str_stuff

src/python/grpcio/grpc/_channel.py

src/python/grpcio/grpc/_common.py

src/python/grpcio/grpc/_cython/_cygrpc/channel.pyx.pxi

src/python/grpcio/grpc/_cython/_cygrpc/credentials.pyx.pxi

src/python/grpcio/grpc/_cython/_cygrpc/records.pyx.pxi

src/python/grpcio/grpc/_cython/_cygrpc/server.pyx.pxi

src/python/grpcio/grpc/_plugin_wrapping.py

src/python/grpcio/grpc/_server.py

src/python/grpcio/grpc/beta/_server_adaptations.py

src/python/grpcio/tests/unit/_compression_test.py

...thon/grpcio/tests/unit/_cython/_cancel_many_calls_test.py

src/python/grpcio/tests/unit/_cython/_channel_test.py

...sts/unit/_cython/_read_some_but_not_all_responses_test.py

src/python/grpcio/tests/unit/_cython/cygrpc_test.py

src/python/grpcio/tests/unit/_empty_message_test.py

src/python/grpcio/tests/unit/_metadata_code_details_test.py

src/python/grpcio/tests/unit/_metadata_test.py

src/python/grpcio/tests/unit/_rpc_test.py

src/python/grpcio/tests/unit/beta/_utilities_test.py

src/python/grpcio/tests/unit/beta/test_utilities.py