Patch: validator that matches against a regular expression

[hugo <gb@…>]

For some cases it's easies to have a validator that just matches against some given regular expression:

class MatchesRegularExpression:
    def __init__(self, regexp, error_message="The format for this field is wrong"):
        self.regexp = regexp
        self.error_message = error_message

    def __call__(self, field_data, all_data):
        if not self.regexp.match(field_data):
            raise validators.ValidationError(self.error_message)

This is actually a validator factory that produces the validator on instantiation.

[Adrian Holovaty]

(In [399]) Fixed #269 -- Added MatchesRegularExpression validator. Thanks, Hugo!