Correct/update import.
Use a simpler, more efficient validator for empty str.
Correct bug in test.
Override is_empty of ValidCSRFToken.

to turn off FancyValidator allowing empty values to pass through by
default.
Remove now unnecessary not_empty=True.

Now that ValidCSRFToken no longer allows empty values to pass through by
default.
Remove Pipe and ConfirmType.

Now that ValidCSRFToken doesn't let empty values through, they are not
longer necessary.