Validate schema with Colander for either uuid or mail are in the request.

gistfile1.py

@deferred
def deferred_check_missing(node, kw):
    try:
        json_request = kw.get("request").json_body
    except ValueError:
        raise Invalid(node, "Malformed JSON provided")

    if "mail" not in json_request and "uuid" not in json_request:
        raise Invalid(node, "Both mail and uuid are missing")

    return None


class ImportSchema(ACLMappingSchema):
    mail = SchemaNode(String(),
        missing=deferred_check_missing,
    )

    uuid = SchemaNode(String(),
        missing=None
    )