List of things to include in next astropy-helpers/package template updates

[astrofrog]

This issue is just a reminder of things we could include in the next batch updates for astropy-helpers and package-template files. Feel free to add more in comments (or edit this):

• Update astropy-helpers
• Remove ez_setup.py
• Update _astropy_init.py
• Update setup.py

Notify/open issues:

• MPLBACKEND is now set to Agg, packages expecting interactive plotting should override it in .travis.yml
• update travis matrix, at least jobs with NUMPY_VERSION<1.13 and ASTROPY_VERSION=stable
• sphinx-astropy as dependency: List of things to include in next astropy-helpers/package template updates #108 (comment)
• six not to be imported from astropy but directly

Next round of issues:

• usage of _ASTROPY_SETUP_ and that whether that tries to import astropy at setup time or not Don't require astropy to be importable at setup.py time astropy#8402 (comment)

With helpers 3.2 update:

• make a note that sphinx-astropy should be listed as a dependency for building the docs.

[bsipocz]

The first 2 can and will be dealt with the usual helpers update procedure.

For the rest, it would be useful to list the stuff that we need to update specifically (a link to the relevant PR in the template would do)

[astrofrog]

@bsipocz - for _astropy_init.py I was thinking of just copying over the whole file from the template to make sure it's up to date, whatever people have in their package (rather than checking for specific changes)

[bsipocz]

oh. So you think it's safe to assume no one did any customization there? Probably that's a fair assumption though (or maybe there is an easy way to compare it to each and every version of that file from the package template, and if it's from any point in the past we can assume it's safe to update).

[astrofrog]

We can check for customizations of the file by comparing to hashes of past versions of that file. This is actually true for all files of the template in fact. I'll try writing a script soon that can do these kinds of checks.

[pllim]

I found that I also had to update RTD requirements file to include sphinx-astropy after update to astropy-helpers 3.1. Not sure how easy it is to hunt down some random RTD requirements file and update it properly; maybe just add a note in this same PR to remind maintainer to check it, is applicable.