Remove python_type from color (this might have some side effects)

sqlalchemy_utils/types/color.py

@@ -17,7 +17,6 @@ class ColorType(types.TypeDecorator, ScalarCoercible):
     """
     STORE_FORMAT = u'hex'
     impl = types.Unicode(20)
-    python_type = colour.Color
 
     def __init__(self, max_length=20, *args, **kwargs):
         # Fail if colour is not found.

tests/types/test_color.py

@@ -18,10 +18,6 @@ class TestColorType(TestCase):
 
         self.Document = Document
 
-    def test_python_type(self):
-        type_ = self.Document.__table__.c.bg_color.type
-        assert type_.python_type == color.colour.Color
-
     def test_color_parameter_processing(self):
         from colour import Color