'``get_output()`` returns the command\'s output.'

def test_get_output(self):

    node = make_sshnode(self)
    temp_file = FilePath(self.mktemp())
    temp_file.setContent('hello!')
    def go():
        return node.get_output(['python', '-c', ("import    sys;    sys.stdout.write(file('%s').read())" % (temp_file.path,))])
    d = deferToThread(go)
    def got_data(data):
        self.assertEqual(data, 'hello!')
    d.addCallback(got_data)
    return d
