Having the ReplaceTrailingDotsWithEllipsis autofix enabled results in an _IndexError: string index out of range_ error whenever an empty source string is used (which is unlikely, but not technically impossible).

This patch solves this problem by first checking for non-emptiness of the source string.

For en_CA@foo it would first try en_CA and fallback to en.

This prevents various problems with non standard language names.

Fixes #318

This value is never used and causes problems with some
MySQL/Django/South version combinations.

The only reason this field originally had NULL attribute and it has it
now removed was migration path, where it was filled in by separate data
migration:

0018 - adds Change.translation field with NULL allowed and default
0019 - fills in Change.translation for all entries
0020 - removes NULL attribute

This fixes #319.

They use wildcard imports.

Hardcoded ones do not work with other databases who might not reset
sequences at test start.

We don't need to test all database backends with Python 2.6.

Sorting then can be broken with some databases.