Modify https://github.com/grpc/grpc/blob/master/src/python/grpcio_tests/tests/interop/methods.py#L47 and throw in some letters in upper-case.
Then run the python custom_metadata interop test.
The test eventually times out.

Expect to exit with exception.

Attached is the client log.
test.txt