Thanks Tim Graham for the review.

On a SyntaxError, made runserver exit with a stacktrace when using
contrib.staticfiles's runserver options such as --nostatic.

Removed unused DatabaseFeatures.driver_supports_timedeltas workaround.

Removed obsolete workarounds from 1aa48898
and dcf3be7a.

Executing a DDL statement during a transaction on backends that don't support
it silently commits, leaving atomic() in an incoherent state.

While schema_editor.execute() could technically be used to execute DML
statements such usage should be uncommon as these are usually performed through
the ORM. In other cases schema_editor.connection.execute() can be used to
circumvent this check.

Thanks Adam and Tim for the review.

Fixed Python 2 regression in 6dbe56ed.

Thanks Simon Charette for the implementation idea.

Thanks Shivang Bharadwaj for the initial patch.

Thanks Carl Meyer and Tim Graham for contributing to the patch.