[1.6.x] Fixed #23123 -- Don't use a bare except in ModelAdmin documentation

Thanks to wkschwartz for the report and to Tim for the patch.

Backport of e5619330e2 from master
[1.6.x] Fixed #20292: Pass datetime objects (not formatted dates) as params to Oracle

This seems worthwhile in its own right, but also works around an Oracle
bug (in versions 10 -- 11.1) where the use of Unicode would reset the
date/time formats, causing ORA-01843 errors.

Thanks Trac users CarstenF for the report, jtiai for the initial patch,
and everyone who contributed to the discussion on the ticket.

Backport of 6983201 from master.
[1.6.x] Added a missing skipUnlessDBFeature for the previous commit.