autopep8: F841 undefined name
Special cases:
- `long` and `unicode` no longer exist in python 3. I added a "# noqa"
comment to avoid warnings.
- `cmp` method no longer exist in python 3. It was used in the
`test/unittest_analyze.py` file in the __cmp__ method. It appears that
when this method is removed, all the tests are still valid. Therefore I
dropped it.