“9f8e4981384d247e461290d7ceb642486663390d”上不存在“python/paddle/v2/fluid/tests/unittests/test_pad_op.py”
For input argument with a list of variables, drop_empty_grad is not allowed because it makes the correspondence bewteen a variable and its gradient ambiguous. Use REGISTER_OP_EX to register the op or call InputGrad(?,false) in GradOpDescMaker.