Created by: Yancey1989

fit_a_line.py run failed with more than 2 pserver instances.

Traceback (most recent call last):
  File "test_fit_a_line.py", line 159, in <module>
    train(False, "fit_a_line.inference.model", False)
  File "test_fit_a_line.py", line 89, in train
    trainers=trainers)
  File "/paddle/build/python/build/lib-python/paddle/fluid/distribute_transpiler.py", line 216, in transpile
    eplist = split_method(send_inputs, pserver_endpoints)
  File "/paddle/build/python/build/lib-python/paddle/fluid/distributed_spliter.py", line 39, in round_robin
    assert (len(varlist) > len(pserver_endpoints))
AssertionError