fix #234: GitHub action api verification

[rorour]

fix #234: GitHub Action verification that HEAD's SHA has passed all actions

Here is something functional. Looking forward to feedback.

• Vars owner and branch are just temporary while I'm developing. I'm testing with rorour/pykern because it has workflow runs on master.
• In order to get the commit sha matching HEAD from the API, I changed the post-merge action to run on master/main instead of the merged branch.
• Using requests because the github3 python library doesn't support actions (add support for actions api sigmavirus24/github3.py#1006)
• Issues to consider:
  • How to handle repos that use main instead of master? I tried to make 'branch' a parameter with default value but that didn't seem to work with pkcli, I got pykern github: error: unrecognized arguments: main
  • How to get the HEAD sha that we're checking against the api? my approach assumes that we have a local copy of the repo, and checks out and pulls master.
  • How to authenticate with github - for now I'm using os.environ['GITHUB_PAT']

[rorour]

@robnagler ready for review

[robnagler]

I think this is ok, but I would like to resolve the conditional complexity.

[robnagler]

Include branch name and sha. Watch for repetition when you do this to the next error message to.

[rorour]

What do you mean by watch for repetition? Should I just print branch name and sha once before all the error checking?

[robnagler]

First step is add the branch and sha to all messages. Then, see what patterns repeat. Then, simplify the repetition.

[rorour]

pksubprocess_test keeps randomly failing on this pr. Do you know what might be causing it?

=================================== FAILURES ===================================
_________________________ test_check_call_with_signals _________________________
Traceback (most recent call last):
  File "/home/runner/work/pykern/pykern/tests/pksubprocess_test.py", line 65, in test_check_call_with_signals
    pksubprocess.check_call_with_signals(cmd, output=o, msg=msg)
  File "/home/vagrant/.pyenv/versions/3.7.2/envs/py3/lib/python3.7/site-packages/_pytest/python_api.py", line 966, in __exit__
    fail(self.message)
  File "/home/vagrant/.pyenv/versions/3.7.2/envs/py3/lib/python3.7/site-packages/_pytest/outcomes.py", line 196, in fail
    raise Failed(msg=reason, pytrace=pytrace)
Failed: DID NOT RAISE <class 'RuntimeError'>
============================== 1 failed in 10.15s ==============================
error: FAILED=1 passed=37

[robnagler]

No, I don't. How would you instrument pksubrocess_test to debug this? How would you debug this more easily?

[rorour]

I think the failing test is unrelated to the changes in this pr, so I can make an issue for it. This pr is ready for re-review. ea3c408

[robnagler]

That's what I was looking for.