My plan is to first write a new test in a new test file that tries to render
all template files of the jinja2 subdirectory once. 

Then I am adding a custom filter called "u" that will
either render a python string object from utf-8 into unicode object
or call str() on other python objects before encoding.

Then adding all "|u" custom filters to the jinja2 template, satisfying
the test.

I've started coding the test using a full setup from db_test_base
which many tests do, but only with one databasebackend.