Allowing default flags in run_flow().

[dhermes]

Resurrects #360. I double checked two different default behaviors to verify this is the "right" way:

>>> # Method 1
>>> flags = argparser.parse_args()
>>> flags
Namespace(auth_host_name='localhost', auth_host_port=[8080, 8090], logging_level='ERROR', noauth_local_webserver=False)
>>> # Method 2 (same result, but takes more code)
>>> import argparse
>>> parser = argparse.ArgumentParser(parents=[argparser])
>>> flags = parser.parse_args()
>>> flags
Namespace(auth_host_name='localhost', auth_host_port=[8080, 8090], logging_level='ERROR', noauth_local_webserver=False)

[nathanielmanistaatgoogle]

Test coverage?

[dhermes]

I was under the assumption that there were no tests for this module, let me double check.

[dhermes]

OK I was wrong, but correct in spirit. The tests for the tools module are essentially 0, and testing run_flow() would increase the size of this PR by a factor of 20, so it should probably be its own thing.

[nathanielmanistaatgoogle]

Okay. I was caught by the -0.03% coverage decrease and for once I looked at it and said "wait, no, that's a real thing and not just noise, this change introduces new code that is definitely not covered".

Merge when you like.

[dhermes]

FWIW I really want some help to sprint through #212 and make any drop below 100% not allowed