Fix URLs like /projects/subproject from 404ing when they don't end with a slash

[ericholscher]

This was hit by users.
You can test it here: https://docs.celeryproject.org/projects/kombu

[ericholscher]

Looks good locally:

-> curl -IL http://test-builds.community.dev.readthedocs.io/projects/subproject
HTTP/1.1 302 Found
Server: nginx/1.17.5
Date: Fri, 10 Apr 2020 21:09:30 GMT
Content-Type: text/html; charset=utf-8
Content-Length: 0
Connection: keep-alive
Location: http://test-builds.community.dev.readthedocs.io/projects/subproject/en/latest/
X-RTD-System-Redirect: True
X-Frame-Options: DENY
X-Content-Type-Options: nosniff
X-XSS-Protection: 1; mode=block
Vary: Accept-Language, Cookie
Content-Language: en
X-Served: Django-Proxito

[davidfischer]

Looks good.

Edit: once the CI is fixed up.

[ericholscher]

We also have an issue with single-single subprojects, eg http://test-builds.community.dev.readthedocs.io/projects/single-version
where they 404 currently, and with that change, it serves the files but all media breaks (because it needs the /)

[humitos]

Looks good to me. I want to understand one the cases added, only.

Test are not passing for some reason as well.

[humitos]

Test are not passing for some reason as well.

Ah, we need to update the matching of the URLs because there is a new attribute now.

[humitos]

Weird... our own build on RTD failed because of timeout. Is our project already that big?