Python 2.5 compatibility

[jaap3]

These changes make raven work again under Python 2.5.

Had to skip the tests for the WSGI middleware (using webob) and zerorpc as those packages themselves aren't python 2.5 compatible.

This pull request includes fixes for issues #161 and #89

[jaap3]

@dcramer Are you interested in merging this, or is Python 2.5 compatibility not one of the goals of raven? The last version for me to work on py25 is raven 1.9.2

[dcramer]

@jaap3 I'm not against 2.5. I actually just forgot about this pull request :)

Looking through it now the one thing I want to understand more is the urlparse changes required, but otherwise it looks pretty good

[jaap3]

Alright cool :). The urlparse changes are because older versions of python/urlparse have trouble parsing custom/unknown schemes (also mentioned in issues #89). By hooking into the the TransportRegistry it's easy to register any custom scheme that urlparse fails to handle on Python < 2.6.5.

Without this raven is unable to parse things like the threaded+http or the mock urls in the testcases.

[jaap3]

I might be wrong on the threaded+http since it seems that the url is already stripped of the threaded part. Still it fixes the issue with dup and the mock protocol used in tests. Since transports are pluggable this seemed like the most sane solution to me.