Thanks Jacek Bzdak for indepdently contributing a similar fix.

This fixes a regression from refs #25496.

This only happens if USE_TZ = False and pytz is installed (perhaps not
the most logical combination, but who am I to jugde?)

Refs #23714 which essentially fixed the same problem when USE_TZ = True.

Thanks Florian and Carl for insisting until I wrote a complete patch.

To improve consistency, sample URL names that had underscores
in them now use dashes instead. That excludes URL names that
have some relation to the code, such as those generated by
the admin.

Thanks guettli for reporting this.

This was a possible confusion source with column name arguments.
Thanks Sergey Fedoseev for the suggestion.

Thanks Iacopo Spalletti for the report and testing.

Added support for ST_Difference/ST_Intersection/ST_SymDifference.