Update astropy-helpers to v3.2.1

[bsipocz]

This is an automated update of the astropy-helpers submodule to v3.2.1. This includes both the update of the astropy-helpers sub-module, and the ah_bootstrap.py file, if needed.

A full list of changes can be found in the changelog.

We also wanted to let you know that we have made new releases of the astropy package-template. You can find the latest cookiecutter template here or if you prefer you can find a rendered version of the template here.

This is intended to be helpful, but if you would prefer to manage these updates yourself, or if you notice any issues with this automated update, please let @bsipocz or @astrofrog know!

Similarly to the core package, the v3.0+ releases of astropy-helpers require Python 3.5+. We will open automated update PRs with astropy-helpers v3.2.x only for packages that specifically opt in for it when they start supporting Python 3.5+ only. Please let @bsipocz or @astrofrog know or add your package to the list in https://github.com/astropy/astropy-procedures/blob/master/update-packages/helpers_3.py

[bsipocz]

First step towards python3 only, we should probably remove the python2 test runs first...

[bsipocz]

Circle CI and travis issues in unrelated and is present on master. See #288

[bsipocz]

I'm merging this PR as it doesn't make things worse then on master and the pytest 5 related failures should be fixed in a separate PR anyway.

[cdeil]

@bsipocz - As far as I know, @keflavich and CASA users still need Python 2 support for the regions package (see #241). If that's the case, we should probably revert this PR?

@keflavich - Please comment.

[keflavich]

Yes, thanks @cdeil. Please keep regions py2.7-compatible at least for a few more months. It's a sad state, I know, but I have scripts that rely on CASA working with this package.

[cdeil]

@bsipocz - Could you either merge #290 or I guess this would also be OK, to avoid messy git history, since this repo isn't very active and it's been less than a day.

git checkout master
git reset --hard e4e74502fb32596c48136f2d7e279c95421570a1
git push -f

[bsipocz]

@keflavich - but do you need python2 support on master? I assumed we already said that moving forward it's ok to be python3 from the CASA point of view.

[bsipocz]

but then I agree that git reset HEAD~1 on master and the force push would still makes sense given that nothing has happened since yesterday.

[keflavich]

Yes, in general that's OK, but regions doesn't really have a stable release at all, so it needs py2 on master. Astroquery is not supporting py2 on any new features, but it will still work on py2 as long as new modules aren't used, right?

[bsipocz]

I'm not sure what stable release means here, v0.4 is a real release and anyone requiring python2 could just stick with it.
Using master of a package doesn't really makes sense in most of the situations anyway as while we try to keep master clean it's not guaranteed to have passing builds, etc while a tag release has that.

[bsipocz]

I've reset this from master, but it still doesn't let me reopen. So will just open another copy of that branch.