Fixed #20354 -- `makemessages` no longer crashes with `UnicodeDecodeError`

Handle the `UnicodeDecodeError` exception, send a warning to `stdout` with the
file name and location, and continue processing other files.
Update GeoDjango testing docs; GeoDjangoTestSuiteRunner is gone.
Update tutorial 5 for test discovery.
Python 2.5 is not relevant to master.
Fixed inconsistent punctuation in tutorial 5.
Merge branch 'master' into ticket-17365-new

* master:
  Fixed inconsistent punctuation in tutorial 5.
  Python 2.5 is not relevant to master.
  Fixed #20354 -- `makemessages` no longer crashes with `UnicodeDecodeError`