Fixed a failing test introduced in 918a16bc4c099ab0cae72a231de3e99e2a9d02cb.

Refs #22307.
Removed an unused variable.
Fixed #20684 -- Added support for HTML5 boolean attributes to form widgets.
Made m2m fields form help_text munging specific to admin widgets.

Refs #9321 and follow-up to e80de93af6a0a21a9063a55c4d6d20e3927243e9.
Removed GeoRSSSitemap

Refs #18531.
Advanced deprecation warnings for 1.8.
Fixed #22313 -- Removed 'u' prefixes from documentation
Fixed #22308 -- Regression from 0f956085.

Rewrote the test for #9479 according to the original ticket.
Fixed #22299 -- Cleanup wizard temp files when possible.

Thanks to @erikr for the review.
Fixed PostGIS test failures.
POC Form.has_error().