tox leading to bad marshal data ValueError

[huntzhan]

________________________ ERROR collecting tests/scheduler/test_scheduler.py ________________________
.tox/py27/lib/python2.7/site-packages/py/_path/local.py:620: in pyimport
>           __import__(modname)
.tox/py27/lib/python2.7/site-packages/_pytest/assertion/rewrite.py:134: in find_module
>       co = _read_pyc(fn_pypath, pyc)
.tox/py27/lib/python2.7/site-packages/_pytest/assertion/rewrite.py:311: in _read_pyc
>           co = marshal.load(fp)
E           ValueError: bad marshal data (unknown type code)
===================================== 12 error in 0.46 seconds =====================================
  ___ _   ___ _    ___ ___
 | __/_\ |_ _| |  | __|   \
 | _/ _ \ | || |__| _|| |) |
 |_/_/ \_\___|____|___|___/

I found a discussion of this problem, and the corresponding solution.