Upgrade bot to be compatible with PyGithub v2.1.1

[laraPPr]

I tested the changes with python 3.8

resolves the following issue: #223

[boegel]

PyGithub 2.1.1 requires Python >= 3.7, so applying this fix implies that the bot will no longer support Python 3.6 (see also failing CI)...

That's painful because Python 3.6 is the default Python in RHEL 8 & derivates, so ideally we retain compatibility with that.

I wonder if there's a smart way in which can check whether or not we need to compare with a datetime instance that includes tzinfo, or not.
Maybe we can easily check which version of PyGithub we're dealing with?

[boegel]

Hmm, I can't find a direct way to check the PyGithub version, but we can do it by proxy: the GithubRetry class was introduced in PyGithub 2.x, so:

[bot@login1 ~]$ python3.6 -m pip list | grep PyGithub
PyGithub (1.56)
[bot@login1 ~]$ python3.6 -c "import github; print(hasattr(github, 'GithubRetry'))"
False

[boegel@login1 ~]$ python3.9 -m pip list | grep PyGithub
PyGithub           2.1.1
[boegel@login1 ~]$ python3.9 -c "import github; print(hasattr(github, 'GithubRetry'))"
True

[boegel]

if ... is False is kind of silly, and positive logic is easier to follow, and there's a lot of copy-pasting, so I would change this to:

    # PyGithub 2.x expects a datetime object with timezone info,
    # PyGithub 1.x requires one without timezone info;
    # see also https://github.com/PyGithub/PyGithub/pull/2565
    if hasattr(github, 'GithubRetry'):
        # PyGithub 2.x
        time_now = datetime.now(timezone.utc)
    else:
        # PyGithub 1.x
        time_now = datetime.utcnow()

    if not _gh or (_token and time_now > _token.expires_at):
        _gh = connect()

[boegel]

lgtm

[trz42]

Did some test runs with Python/3.6.8 and Python/3.9.16. See trz42/software-layer#67

Looks good.