> I haven’t heard any arguments against this option yet, and it didn’t break any tests.

Pre patch:

>>> urljoin('mailto:foo@', 'bar.com')
'bar.com'

Post patch:

>>> urljoin('mailto:foo@', 'bar.com')
'mailto:bar.com/bar.com'

I'm taking an educated guess here based on a marginal amount of research (there are just a few registered schemes at http://www.iana.org/assignments/uri-schemes/uri-schemes.xhtml that should be understood), but it /seems/ like perhaps the current behaviour is intended to safeguard against joining non-hierarchical schemes in which case you'd get nonsensical values. It does seem a little odd to me, but I definitely prefer the former behaviour to the latter.

I think that short term, Madison's suggestion about documenting uses_relative would be an easy win and can be applied to all branches. Long term though, I think it would be nice to have a generalized urljoin() method that accounts for most (if not all) classifications of url schemes.

Thoughts?