[IMP] fix a typo, even if it doesn't matter

(odo would probably say something like 'stop acting nitpicky !' ;))

bzr revid: abo@openerp.com-20130201165015-l3dtvil3u59kqzf7

openerp/tests/addons/test_exceptions/models.py

@@ -29,5 +29,5 @@ class m(openerp.osv.osv.Model):
         raise Exception('AccessDenied')
 
     def generate_undefined(self, cr, uid, ids, context=None):
-        self.surely_undefined_sumbol
+        self.surely_undefined_symbol
 # vim:expandtab:smartindent:tabstop=4:softtabstop=4:shiftwidth=4: