close #511810: bad rql generated when looking for vocabulary for a relation on an entity which doesn't exist (yet)
technical details:
* add a graph of linked variables in the RRQLExpression instance
* modify rql rewriter to remove relations where an unexistant
variable and or a variable linked to an unexistant variable is used.
* activate this feature in Entity.unrelated_rql if the entity doesn't exists yet
"""pre 3.2 bw compat
:organization: Logilab
:copyright: 2001-2009 LOGILAB S.A. (Paris, FRANCE), license is LGPL v2.
:contact: http://www.logilab.fr/ -- mailto:contact@logilab.fr
:license: GNU Lesser General Public License, v2.1 - http://www.gnu.org/licenses
"""
# pylint: disable-msg=W0614,W0401
from warnings import warn
warn('moved to cubicweb.entity', DeprecationWarning, stacklevel=2)
from cubicweb.entity import *
from cubicweb.entity import _marker