Replace old mimeparse package with python-mimeparse

[agjohnson]

Note! These packages occupy the same namespace. You might need to uninstall
mimeparse and reinstall python-mimeparse.

Refs #3570

Deployment notes

The old package mimeparse is not py3 compatible, but django-mailgun brings in it's own dependency of python-mimeparse, which is py3 compatible. This might not affect our RS cluster, but does affect our Azure cluster. Actions required on our Azure cluster were to manually remove mimeparse and install python-mimeparse, as these packages are forks and provide the same namespace. We aren't upgrading the django-mailgun package here though, so might not be required for RS deployments.

[humitos]

Sounds good!

Reading the referenced issue seems that it doesn't fail on startup but by hitting a specific URL. It may be good to have a simple test that checks that URL (or a couple of similar) works, don't you think?

[agjohnson]

Perhaps yeah. This was on sending an email. I'm not sure when i'll be able to get back to adding a test for this. maybe someone else can take it or we can create an issue for it.

[humitos]

There is no need to create a test or anything like that. The endpoint with the problem was deleted completely some time ago.

One thing I noticed is that python-mimeparse is not a dependency of our project (grepping the whole code looking for mimeparse gave me no results) so I'd say that we should completely remove python-mimeparse from our requirement.txt file and leave the dependency manager to solve it and install the one that it's required for the thirdparty library that needs it (tastypie or the one you found when sending emails)

[agjohnson]

That makes more sense, yeah. I'll update here.