Run collectstatic before the tests in CI

This stops WhiteNoise from emitting warnings about STATIC_ROOT not
existing.
The alternative would be to set WHITENOISE_AUTOREFRESH = True in the
settings. We currently don't have any settings that are only applied
in CI and I think it makes sense to keep it that way to have the test
environment as close to production as possible.

See evansd/whitenoise#191

Signed-off-by: Haiko Schol <hs@haikoschol.com>

.travis.yml

@@ -16,6 +16,7 @@ before_script:
   - ./manage.py migrate
 
 script:
+  - ./manage.py collectstatic
   - pytest
 
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