Fixed undefined name 'file' in Python3.

Signed-off-by: Kouhei Maeda <mkouhei@palmtb.net>
Supported tox argument in python setup.py test.

Signed-off-by: Kouhei Maeda <mkouhei@palmtb.net>
Enabled pychecker.

Signed-off-by: Kouhei Maeda <mkouhei@palmtb.net>