[GMG-Devel] cyclic imports

[Sebastian Spaeth]

Whenever I modify things, I have to fight cyclic imports in MediaGoblin. 
This is an issue that we really need to think about. Consider this:

I want to give better error message in the case of csrf failures. To do 
so I modify
GMG.meddlewares.csrf to return a GMG.tools.response:render_error().


1) tools.response imports tools.template to get access to
   render_template()
2) tools.template imports meddlewares.csrf to get access to
   render_csrf_token().
3) meddlewares.csrf imports tools.response to get access to
   render_error()
4) BANG BOOM CRASH. ImportError!

How can we solve this issues in this specific and the general case? Here 
I could imagine to solve/fix this by splitting CSRF into a 
meddlewares.csrf (which does the checking) and a tools.csrf (which does 
the actual rendering of the token). But that would split CSRF 
functionality over 2 files. (we could also put it into tools.template 
rather than tools.csrf).

Sebastian