Fixed #19905 -- Fixed leakage of file descriptors in form wizard.
Removed an unused import
Note that the stdlib's version of pbkdf2_hmac will also be used in the upcoming Python 2.7.8 release
Revert "Making SQL management commands migration aware."

This reverts commit cb9c9a7b5879671053c7d2ad6e79943a8814b274.
Fixed #22659 -- Prevent model states from sharing field instances.

Thanks to Trac alias tbartelmess for the report and the test project.