Add psycopg3 support

Fixes #130

Author: bufke

bitfield/types.py

@@ -260,5 +260,6 @@ def get_label(self, flag):
     from django.db.backends.postgresql.base import Database
     Database.extensions.register_adapter(Bit, lambda x: Database.extensions.AsIs(int(x)))
     Database.extensions.register_adapter(BitHandler, lambda x: Database.extensions.AsIs(int(x)))
-except ImproperlyConfigured:
+# Ignore in psycopg3 where there is no Database.extensions nor any need to adapt types
+except (ImproperlyConfigured, AttributeError):
     pass