[py3k] replace 'unicode' with 'cubicweb._'

schema.py

@@ -5,7 +5,11 @@
 :contact: http://www.logilab.fr/ -- mailto:contact@logilab.fr
 """
 __docformat__ = "restructuredtext en"
-_ = unicode
+
+try:
+    from cubicweb import _
+except ImportError:
+    _ = unicode
 
 # pylint: disable-msg=E0611,F0401
 from yams.buildobjs import (SubjectRelation, RelationType, EntityType,

views/email.py

@@ -5,7 +5,11 @@
 :contact: http://www.logilab.fr/ -- mailto:contact@logilab.fr
 """
 __docformat__ = "restructuredtext en"
-_ = unicode
+
+try:
+    from cubicweb import _
+except ImportError:
+    _ = unicode
 
 from logilab.mtconverter import xml_escape