Fixed #19634 -- Added proper __hash__ methods.

Classes overriding __eq__ need a __hash__ such that equal objects have
the same hash.

Thanks akaariai for the report and regebro for the patch.

django/db/models/fields/files.py

@@ -30,7 +30,6 @@ class FieldFile(File):
         return not self.__eq__(other)
 
     def __hash__(self):
-        # Required because we defined a custom __eq__.
         return hash(self.name)
 
     # The standard File contains most of the necessary properties, but