DEPS: drop Python 3.7 and NumPy 1.17 from tests (#41678)
closes #41678

Most of the new minimum support versions were released between Oct 14, 2019, Python 3.8's initial release date, and June/July 2020.
Thanks @fangchenli for getting this started. To close the issue, are you planning to update the release notes in this PR too? > Thanks @fangchenli for getting this started. To close the issue, are you planning to update the release notes in this PR too?

I'll update the doc at last. could update this to `--py38-plus`

https://github.com/pandas-dev/pandas/blob/0b68d87a4438a13f14a2ed5af2e432df02eb0b2c/.pre-commit-config.yaml#L59-L63 > could update this to `--py38-plus`

I think maybe code changes should be a follow-on. This PR should probably just be the ci setup and docs. > update the release notes in this PR too?

I should have said install.rst too.

I think it would be easier for reviewers to see the significant changes, but I also appreciate that while getting things working is an additional burden, so add when ready.

 once we do this, we won't be releasing from master until at least 26 December. Historically, we have had 6 monthly releases (except for 0.22, which was a special case for a api breaking change) so shouldn't be an issue. Are we ready for this? > once we do this, we won't be releasing from master until at least 26 December. Historically, we have had 6 monthly releases (except for 0.22, which was a special case for a api breaking change) so shouldn't be an issue. Are we ready for this?

yep this is fine this early. going to have a look. https://github.com/pandas-dev/pandas/pull/41989/checks?check_run_id=2984645939 random failure? > https://github.com/pandas-dev/pandas/pull/41989/checks?check_run_id=2984645939 random failure?

Looks like a flaky test. thanks @fangchenli very nice!