'Test the L{ServerError} error: when the server sends a B{SERVER_ERROR}
token, the originating command fails with L{ServerError}, and the error
contains the text sent by the server.'

def test_serverError(self):

    a = 'eggspamm'
    d = self.proto.set('foo', a)
    self.assertEqual(self.transport.value(), 'set    foo    0    0    8\r\neggspamm\r\n')
    self.assertFailure(d, ServerError)
    def check(err):
        self.assertEqual(str(err), repr('zomg'))
    d.addCallback(check)
    self.proto.dataReceived('SERVER_ERROR    zomg\r\n')
    return d
