ValueError: Unknown type "version_range"

[mythmon]

This is caused by me changing the name of the filter object, and by me having created some testing recipes a while ago. We should handle this error somehow. Perhaps by having a check that all recipes have valid filter object types and updating this recipe in a migration.

https://sentry.prod.mozaws.net/operations/normandy-stage/issues/8207524/

ValueError: Unknown type "version_range.
(17 additional frame(s) were not displayed)
...
  File "rest_framework/serializers.py", line 675, in to_representation
    self.child.to_representation(item) for item in iterable
  File "rest_framework/serializers.py", line 675, in <listcomp>
    self.child.to_representation(item) for item in iterable
  File "rest_framework/serializers.py", line 513, in to_representation
    attribute = field.get_attribute(instance)
  File "rest_framework/fields.py", line 443, in get_attribute
    return get_attribute(instance, self.source_attrs)
  File "rest_framework/fields.py", line 93, in get_attribute
    instance = getattr(instance, attr)

ValueError: Unknown type "version_range.