'L{app.AppLogger} using a legacy logger observer still works, wrapping
it in a compat shim.'

def test_legacyObservers(self):

    logs = []
    logger = app.AppLogger({})
    @implementer(LegacyILogObserver)
    class LoggerObserver(object, ):
        '\n                                                An    observer    which    implements    the    legacy    L{LegacyILogObserver}.\n                                                '
        def __call__(self, x):
            '\n                                                                Add    C{x}    to    the    logs    list.\n                                                                '
            logs.append(x)
    logger._observerFactory = (lambda : LoggerObserver())
    logger.start(Componentized())
    self.assertIn('starting    up', textFromEventDict(logs[0]))
    warnings = self.flushWarnings([self.test_legacyObservers])
    self.assertEqual(len(warnings), 0)
