[web] safety belt to avoid overriding pageid with loadxhtml()
HtmlHeaders.define_var() now accepts a third optional 'override' paramater.
If set to False, the variable won't be evaluated if it's already defined
in the page.
"""pre 3.0 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.schema', DeprecationWarning, stacklevel=2)
from cubicweb.schema import *