Fixes collection error with Python 3.5.3 (Travis):
testing/test_parseopt.py:2: in <module>
import distutils.spawn
.tox/py35-coverage/lib/python3.5/distutils/__init__.py:4: in <module>
import imp
.tox/py35-coverage/lib/python3.5/imp.py:33: in <module>
PendingDeprecationWarning, stacklevel=2)
E PendingDeprecationWarning: the imp module is deprecated in favour of importlib; see the module's documentation for alternative uses
Build log: https://travis-ci.org/blueyed/pytest/builds/648305304