Stop WhiteNoise warning about STATIC_ROOT not existing during tests

[reupen]

Description of change

This is related to evansd/whitenoise#191, but that fix doesn't work as settings.DEBUG gets set to False when running tests.

This simply sets the two settings that are normally set from settings.DEBUG to True, which then triggers the fix in WhiteNoise. I don't expect any real effect on the tests as there wouldn't normally be requests for static files in them.

Checklist

• Has a new newsfragment been created? Check changelog/README.rst for instructions
• Have any relevant search models been updated?
• Have any relevant fixtures (fixtures/test_data.yaml) been updated?
• Have any relevant select-/prefetch-related field lists in the views and search apps been updated?
• Has the admin site been updated (for new models, fields etc.)?
• Has the README been updated (if needed)?

[codecov]

Codecov Report

Merging #1157 into develop will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff            @@
##           develop    #1157   +/-   ##
========================================
  Coverage    96.58%   96.58%           
========================================
  Files          234      234           
  Lines         6539     6539           
  Branches       612      612           
========================================
  Hits          6316     6316           
  Misses         154      154           
  Partials        69       69

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