'Return a definition of the fields that ignores field names and
what related fields actually relate to. Used for detecting renames (as,
of course, the related fields change during renames).'

def only_relation_agnostic_fields(self, fields):

    fields_def = []
    for (name, field) in sorted(fields):
        deconstruction = self.deep_deconstruct(field)
        if (field.remote_field and field.remote_field.model):
            del deconstruction[2]['to']
        fields_def.append(deconstruction)
    return fields_def
