Don't initialize PostGIS-specific stuff for non-db connections

Refs #16969.
Fixed #21383 -- Added request details in SuspiciousOperation messages
Recommended flake8 to check coding style.
Fixed #21378 -- Updated tutorial02 for how to override admin site header.
Fixed versionadded misuse in the admin documentation.
flake8 fix
Fixed doc typo.
Fixed #21398 -- Fixed BCryptSHA256PasswordHasher with py-bcrypt and Python 3.

Thanks arjan at anymore.nl for the report.
Fixed spelling of compatibility.
Fixed #14800 -- Suppressed WSGIRequestHandler message filtering

Filtering out static file requests in runserver has been judged
arbitrary and can hide some debugging-related activity.
Thanks Roy Smith for the report and Aymeric Augustin for the
review.
Fixed #21372 -- Corrected docs regarding translating LANGUAGES.

Corrected LANGUAGES documentation on how to translate language
names. Now using django.utils.translation.ugettext_lazy instead
of a dummy gettext() function.

Thanks to Salvatore for the report.
Fixed typo in tutorial 2; refs #21418.
added description of MySQL Connector/Python

Reorganized the MySQLdb section into a "MySQL DB API Drivers" section that describes both MySQLdb and MySQL Connector/Python. Included description of the Django adaptors for these DB API drivers.
Fixed #21351 -- Replaced memoize with Python's lru_cache.

Replaced the custom, untested memoize with a similar decorator from Python's
3.2 stdlib. Although some minor performance degradation (see ticket), it is
expected that in the long run lru_cache will outperform memoize once it is
implemented in C.

Thanks to EvilDMP for the report and Baptiste Mispelon for the idea of
replacing memoize with lru_cache.
Fix syntax error under Python 3.2.
Fixed #21420 -- Autoreloader on BSD with Python 3.

Thanks Bouke Haarsma for the report.
Merge pull request #1906 from DanSears/master

Added description of MySQL Connector/Python
Fixed #9523 -- Restart runserver after compiling apps translations

Django also uses locales provided by apps, which also might change. Also when
i18n is disabled, there is no need for watching translation files.
Fixed #20990 -- Ensured unicode paths in compilemessages

Thanks Gregoire Astruc for the report and furins for the review.
Fixed #21388 -- Corrected language code for Frisian