Description

The page on virtualenv in the development documentation (which I believe I might have originally written most of), while still a good thing to have, is pretty outdated and should be cleaned up at some point. A few points to highlight

• In the usage instructions it still mentions the --distribute flag which has long been deprecated and is no longer relevant.
• At the time of its original writing I don't think conda existed yet, or was not widely used. For most beginners I would recommend conda (which we do elsewhere in the documentation) but it would be good here to clarify the relationship between conda environments and virtualenv environments (and why the former precludes use of the latter).
• It would also be good to mention venv more prominently since it is more widely used these days, but also clarify its relationship with virtualenv (and why the latter is more flexible), but the former is also still useful in a pinch.
• Maybe some mention of Pipenv?
• Clean up most of the documentation on using virtualenv with IPython; although there already is a notice to this effect, most of this documentation is long obsolete and would better be removed to reduce confusion. Still, some note on how to use IPython/jupyter notebooks in a virtualenv would be good to have.

Update: It turns out there is also already a newer page on working with different types of virtual environments: https://docs.astropy.org/en/latest/development/workflow/virtual_pythons.html#virtual-envs I would probably just integrate I listed above that's missing from that page, and then either remove the old page or change it to a redirect to the new one.