Fix b8ba7fe6.

Obvious syntax error that viciously passed pylint.
(cherry picked from commit 192de42b)

slapos/recipe/request.py

@@ -131,7 +131,7 @@ class Recipe(object):
           options['instance-guid'] = self.instance.getInstanceGuid()
           # XXX: deprecated, to be removed
           options['instance_guid'] = self.instance.getInstanceGuid()
-        except slapmodule.ResourceNotReady, AttributeError:
+        except (slapmodule.ResourceNotReady, AttributeError):
           # Backward compatibility. Old SlapOS master and core don't know this.
           self.logger.warning("Impossible to fetch instance GUID.")
     except (slapmodule.NotFoundError, slapmodule.ServerError, slapmodule.ResourceNotReady) as exc: