def test_beforeTriggerException(self):
        events = []

        class DummyException(Exception):
            pass

        def raisingTrigger():
            raise DummyException()

        self.event.addTrigger('before', raisingTrigger)
        self.event.addTrigger('before', events.append, 'before')
        self.event.addTrigger('during', events.append, 'during')
        self.event.fireEvent()
        self.assertEqual(events, ['before', 'during'])
        errors = self.flushLoggedErrors(DummyException)
        self.assertEqual(len(errors), 1)
Called when a drag operation is starting on a tree item.
dataset/ETHPy150Open kuri65536/python-for-android/python-modules/twisted/twisted/test/test_internet.py/ThreePhaseEventTests.test_beforeTriggerException--crossover with--dataset/ETHPy150Open enthought/pyface/pyface/viewer/tree_viewer.py/TreeViewer._on_tree_begin_drag