[migration] Skip virtual rtypes when adding relation definition through add_cube Virtual rtypes should be skipped as they are added dynamically on loading schema. Those are skipped by e.g. schema serialisation or add_entity_type, do the same thing here.

.. _req_module:

:mod:`cubicweb.req`
===================

.. automodule:: cubicweb.req

    .. autoexception:: FindEntityError

    .. autoclass:: RequestSessionBase
        :members: