Upgrade to Python 3.8 as minimal required version.

[apollo13]

Python 3.7 is EOL and according to the readme only "active" python versions are supported. I think I found all occurrences of python 3.7 :)

[apollo13]

@microsoft-github-policy-service agree

[apollo13]

One thing that this PR does not do is update NOTICE.txt, seems as if zipp and colorama is no longer required according to pip-compile

EDIT:// yeah colorama is only required on windows: https://github.com/pytest-dev/pytest/blob/54623f0f33c367e19c4041d30f11f71787e30719/setup.cfg#L50 -- if this is wanted, someone with a windows machine would have to regenerate the requirements :)

[apollo13]

Okay, the windows tests are failing due to colorama not being in the generated requirements. Can someone with windows recreate those files? Personally I think the whole approach is flawed since the generated lock files are environment specific… In the worst case linux could require a library named X and windows a library named Y

[karthiknadig]

I will generate.