[IMP] error-level log when non-stored function field without fnct_search is searched

holding off on blowing up an error just yet, but it might be a good idea in the end

bzr revid: xmo@openerp.com-20120802150837-3qvgg3e5pmfeqmk0

openerp/osv/expression.py

@@ -474,6 +474,10 @@ class expression(object):
                     # the function field doesn't provide a search function and doesn't store
                     # values in the database, so we must ignore it : we generate a dummy leaf
                     self.__exp[i] = TRUE_LEAF
+                    _logger.error(
+                        "The field '%s' can not be searched: non-stored "
+                        "function field without fnct_search",
+                        field.string)
                 else:
                     subexp = field.search(cr, uid, table, left, [self.__exp[i]], context=context)
                     if not subexp: