1In this directory:
2- py2_test_grammar.py -- test file that exercises most/all of Python 2.x's grammar.
3- py3_test_grammar.py -- test file that exercises most/all of Python 3.x's grammar.
4- infinite_recursion.py -- test file that causes lib2to3's faster recursive pattern matching
5  scheme to fail, but passes when lib2to3 falls back to iterative pattern matching.
6- fixes/ -- for use by test_refactor.py
7