AttributeError when use pygram.python_grammar_no_print_statement

[ipfans]

I am trying to port yapf to awpa, but I got a error about pygram.python_grammar_no_print_statement:

  File "projects/yapf/yapf/__init__.py", line 39, in <module>
    from yapf.yapflib import yapf_api
  File "projects/yapf/yapf/yapflib/yapf_api.py", line 42, in <module>
    from yapf.yapflib import blank_line_calculator
  File "projects/yapf/yapf/yapflib/blank_line_calculator.py", line 29, in <module>
    from yapf.yapflib import pytree_utils
  File "projects/yapf/yapf/yapflib/pytree_utils.py", line 82, in <module>
    _GRAMMAR_FOR_PY3 = pygram.python_grammar_no_print_statement.copy()
AttributeError: module 'awpa.pygram' has no attribute 'python_grammar_no_print_statement'

I checked that it should work as https://github.com/pyga/awpa/blob/master/awpa/refactor.py#L198, So am I missing something? How can I fix this error?