TST: Test against dev version of astropy (and other important upstream dependencies)

[pllim]

As far as I can tell, the CI is only pulling this for astropy:

PyAutoGalaxy/requirements.txt

Line 2 in 449d5a1

astropy>=3.0.0

Which means you are only testing against the latest astropy release. Adding a test suite to test against development version of astropy would future-proof your code and prevent surprise on your end when new version of astropy is released.

If testing against dev is too much for you, at least test against pre-release (i.e., release candidate) when it is available (e.g., pip install astropy -U --pre).

Bonus: Also test against oldest version of important dependencies that you claim you support. For instance, I have doubt that your code really works for astropy 3.0 as you claim in your requirements file.

astropy/astropy.github.com#491 (comment)