Virtualenv and library fun

Doing python development means using virtualenv, which is wonderful.  Still, sometimes you find a gotcha that trips you up.

Today, for whatever reason, inside a venv inside a brand new Ubuntu 14.04 install,  I could not see a system-wide install of pywsman (installed via sudo apt-get install python-openwsman)

For example:
mrda@host:~$ python -c 'import pywsman'

# Works

mrda@host:~$ tox -evenv --notest

(venv)mrda@host:~$ python -c 'import pywsman'

Traceback (most recent call last):

  File "<string>", line 1, in <module>

ImportError: No module named pywsman

# WAT?

Let's try something else that's installed system-wide

(venv)mrda@host:~$ python -c 'import six'

# Works

Why does six work, and pywsman not?

(venv)mrda@host:~$ ls -la /usr/lib/python2.7/dist-packages/six*

-rw-r--r-- 1 root root  1418 Mar 26 22:57 /usr/lib/python2.7/dist-packages/six-1.5.2.egg-info

-rw-r--r-- 1 root root 22857 Jan  6  2014 /usr/lib/python2.7/dist-packages/six.py

-rw-r--r-- 1 root root 22317 Jul 23 07:23 /usr/lib/python2.7/dist-packages/six.pyc

(venv)mrda@host:~$ ls -la /usr/lib/python2.7/dist-packages/*pywsman*

-rw-r--r-- 1 root root  80590 Jun 16  2014 /usr/lib/python2.7/dist-packages/pywsman.py

-rw-r--r-- 1 root root 293680 Jun 16  2014 /usr/lib/python2.7/dist-packages/_pywsman.so

The only thing that comes to mind is that pywsman wraps a .so

A work-around is to tell venv that it should use the system-wide install of pywsman, like this:

# Kill the old venv first

(venv)mrda@host:~$ deactivate

mrda@host:~$ rm -rf .tox/venv

Now startover

mrda@host:~$ tox -evenv --notest --sitepackages pywsman

(venv)mrda@host:~$ python -c "import pywsman"

# Fun and Profit!