Pep8 fixes

Author: zbyte64

graphene_django/rest_framework/serializer_converter.py

@@ -141,7 +141,7 @@ def convert_serializer_field_to_list_of_string(field):
 
 
 @get_graphene_type_from_serializer_field.register(serializers.ChoiceField)
-def convert_serializer_field_to_list_of_string(field):
-    #enums require a name
+def convert_serializer_field_to_enum(field):
+    # enums require a name
     name = field.field_name or field.source or 'Choices'
     return convert_choices_to_named_enum_with_descriptions(name, field.choices)