Fail testing pep8 with travis-ci

I use travis-ci for GitHub, but test_pep8 failed.

$ pip install -r requirements.txt --use-mirrors
Downloading/unpacking pep8 (from -r requirements.txt (line 1))
  Downloading pep8-1.3.3.tar.gz
  Running egg_info for package pep8
Successfully installed pep8 minimock
Cleaning up...
$ nosetests
ERROR: tonicdnscli.tests.test_pep8.test_check_pep8
Traceback (most recent call last):
  File "/home/travis/virtualenv/python2.7/local/lib/python2.7/site-packages/nose/", line 197, in runTest
  File "/home/travis/builds/mkouhei/tonicdnscli/src/tonicdnscli/tests/", line 25, in test_check_pep8
    runner = pep8.input_file
    AttributeError: 'module' object has no attribute 'input_file'

Ran 17 tests in 0.070s

FAILED (errors=1)

Done. Build script exited with: 1

Cause is version of pep8 module. Travis-ci’s is 1.3.3, but Debian GNU/Linux Sid as my environment is 1.2. So I have appended version of pep8 to requirements.txt.