Snippets backed by Mercurial cannot be cloned by HTTPS (404: Not Found) (BB-16165)

Snippets that use Mercurial to version files cannot be cloned using HTTPS right now, even though UI suggests that everything should work fine.

Example: clicking on the Clone button for https://bitbucket.org/snippets/seanfarley/98ggg/hg-test-output and choosing HTTPS shows hg clone https://bitbucket.org/snippets/seanfarley/98ggg/hg-test-output. Doing that results in:

$ hg clone https://bitbucket.org/snippets/seanfarley/98ggg/hg-test-output
abort: HTTP Error 404: Not Found

At the same time, cloning that snippet with SSH works, but to distribute useful snippets it's obviously not an option, because it requires people to set up keys first.