The solution sketched in my roundup-r4962-issue811-ber1.patch
will not be good enough. The problem is: functions like .plain() 
will be called from within templating.py as well, so we get a mixture
of str and unicode objects and some functions do not like unicode 
objects.
For example urllib.quote will not like them and barf.

I've also tested solutions using functions like .plainu(), but this will get too 
ugly. So I believe the solution should be to use a custom jinja2 filter to do 
unicode conversion on each variable call. 

Note that some objects will just be called from jinja2 and then use str() to 
get its string value. Example {{context.title}}