The overridden url property is no longer necessary.

The issue which the property was circumventing was fixed in django revision 600aa6679ed98d132fc378dfa205f482a58cceb1 (https://github.com/django/django/commit/090ff642043a2ca7d69e475f721eab4d68f6572b#django/core/files/storage.py)

If used with storages that return urls that specify the protocol (ex: http://foo.com/bar#comment)
then the overridden url property quotes the protocol column separator and generates the following invalid url: u'http%3A//foo.com/bar%23comment'