Make covers.py compatible with web.py cgi.FieldStorage removal

[scottbarnes]

Closes #8147

NOTE: This is blocked pending an update to web.py. We have a few proposed solutions for that. Here's one: webpy/webpy#773.

Fix.

This changes covers.py to reflect the changed field names brought on by web.py's switch to multipart.

Deploy Notes

This will affect every request made on the website + cover uploads. We'll want to monitor after deploying (and also try on staging)

Technical

Some field names changed, as the diff will show.

Additionally, the web.py version in requirements.txt has been pinned to the commit with the cgi.FieldStorage change: webpy/webpy@ed3e92c.

Testing

• Add a cover;
• Delete a cover; and
• Generally use the site every page load goes through the changes to web.py, and although all the tests pass here, it's possible there's some changed functionality somewhere.

Stakeholders

@mekarpeles
@tfmorris

[scottbarnes]

Note: This will need to update requirements.txt because this current PR will break things if used with the prior version of web.py.

[scottbarnes]

I am investigating a problem with this PR and webpy v0.70.

[tfmorris]

It looks like there's a discrepancy between file here and filename in https://github.com/webpy/webpy/blob/master/web/webapi.py#L456

The FIXME there should probably be addressed/removed, as well.

[tfmorris]

@scottbarnes Is this still needed or is the new webpy update a drop-in replacement now?

[scottbarnes]

@scottbarnes Is this still needed or is the new webpy update a drop-in replacement now?

Alas, it is still needed.

[scottbarnes]

@mekarpeles, I'm sorry for being a bit slow, but what sort of input are you looking for?