I can run all tests from the roundup source directory
without problems with locale LC_MESSAGES=de_DE.UTF-8.

However I do not have roundup installed in the system
so in roundup/i18n.py find_locales() works and gets me 'de' among 
others, but get_translation() will not find ./locale/de.po in my case, 
because tracker_home is empty. 

My hypothesis is that Benni has an installed roundup in the system
files and uses a German locale, so i18n find his locale.
If I add tracker_home='.' to i18n.py or install roundup in the system
I can reproduce the problem.

Potential solution: Make the test explicitely disable translations.
Suggested in addition: somehow add the source code dir "locale" to the 
search directories for the tests, this would enable i18n tests
and would allow to test that running the non-i18n tests are actually 
independent from a system installed roundup.

Workaround: Disable all translations for running the tests, e.g.
by changing the following line at the bottom of roundup/i18n.py to
 translation = 
get_translation(translation_class=RoundupNullTranslations)