'get_storage_class raises an error if the requested class don\'t exist.'

def test_get_nonexisting_storage_class(self):

    self.assertRaisesErrorWithMessage(ImproperlyConfigured, 'Storage    module    "django.core.files.storage"    does    not    define    a    "NonExistingStorage"    class.', get_storage_class, 'django.core.files.storage.NonExistingStorage')
