Minor cleanups in templates test imports
Added test runner option to skip Selenium tests (#19854).
Merge pull request #781 from zsiciarz/ticket_19854

Fixed #19854 -- Added test runner option to skip Selenium tests
Fixed #15877 -- Improved exception when ModelForm has no model class

Thanks theaspect at gmail.com for the report and volrath for the
patch.
Fixed errors introduced in 21f333bcefccc151d6439246f8203d609ab6ca79. Refs #17751
Fixed errors introduced in 664855b74e1f417384dc7aef35a3df5f86db52d6
Changed %r to %s in get_language_info error message.
Merge pull request #791 from khalas/ticket_19811

Changed %r to %s in get_language_info error message