enable no printing to stdout during auth flow (#203)
enable no printing to stdout during auth flow (#203)

Currently, `run_console` and `run_local_server` unconditionally print a newline to `stdout` even when `authorization_prompt_message` is empty.

This proposed change checks whether printing is actually desired, and if not, prints nothing.

googleapis/google-auth-library-python-oauthlib,googleapis/google-auth-library-python-oauthlib