[PATCH] django.core.urlresolvers.reverse fails sometimes.

[Sebastian Noack]

If you have a url pattern, containing...

• nested groups
• not-matching groups
• look-ahead or look-behind groups

...django.core.urlresolvers.reverse will fail, because of following reasons:

• To replace the groups re.sub with r'\(([^{)]+)\)' is used, which matches only until the first ')', doesn't matter how much groups are nested.}
• All groups which are no named groups are assumed to be positional groups, regardless if they might be not-matching, look-ahead or look-behind groups.