class MissingType(object):
    pass


try:
    # Postgres fields are only available in Django with psycopg2 installed
    # and we cannot have psycopg2 on PyPy
    from django.contrib.postgres.fields import (ArrayField, HStoreField,
                                                JSONField, RangeField)
except ImportError:
    ArrayField, HStoreField, JSONField, RangeField = (MissingType,) * 4