For some reason I'm getting this error when trying to import `gevent` inside my docker container:

```
# python
Python 2.7.10 (default, Oct 14 2015, 16:09:02)
[GCC 5.2.1 20151010] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import gevent

```

```none
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/local/lib/python2.7/dist-packages/gevent/__init__.py", line 51, in <module>
    from gevent.hub import get_hub, iwait, wait
  File "/usr/local/lib/python2.7/dist-packages/gevent/hub.py", line 31, in <module>
    from gevent._util import _NONE
ImportError: cannot import name _NONE
>>>

```

Which is odd because `_util.py` exists, it's in the `dist-packages/gevent` directory. When I did a `pip install` on another system, it works fine.

Anyone have any ideas what might be going on?