title: import error: no module named bson
body: <p>I'm trying to import <code>json_util</code> in my environment file:</p>
  
  <pre><code>from bson import json_util
  </code></pre>
  
  <p>I get this import error: <code>no module named bson</code>.</p>
  
  <p>I tried to pip install and uninstall pymongo and bson - but nothing seemed to help. I found out that the bson package is included in pymongo so I installed it explicitly and then I received an <code>EPOCH_AWARE</code> import error. </p>
  
  <p>Currently, only pymongo is installed. It works when I force the virtual environment by using this line: </p>
  
  <pre><code>#subprocess.Popen(['/home/.virtualenvs/simple_worker/bin/python', fileName])
  </code></pre>
  
  <p>But when I try to run it through the os like this:</p>
  
  <pre><code>os.system('PYTHON_ENV=%s python %s' % (env, fileName))
  </code></pre>
  
  <p>I get this import error on bson.</p>
  
  <p>Edit: Here is the pip list output</p>
  
  <pre><code>(simple_worker) ➜ worker  pip list                                                                                         ✭ ✱
  apache-libcloud (0.17.0)
  backports.ssl-match-hostname (3.4.0.2)
  gnureadline (6.3.3)
  google-api-python-client (1.3.1)
  httplib2 (0.9.2)
  ipdb (0.8)
  ipython (2.3.1)
  mock (1.0.1)
  oauth2client (1.5.1)
  pbr (0.10.7)
  pika (0.9.14)
  pip (8.0.2)
  psutil (2.2.0)
  py (1.4.26)
  pyaml (15.2.1)
  pyasn1 (0.1.7)
  pyasn1-modules (0.0.5)
  pymongo (3.2.1)
  pytest (2.6.4)
  pytest-mock (0.4.0)
  pytz (2015.4)
  PyYAML (3.11)
  redis (2.10.3)
  requests (2.8.0)
  rsa (3.1.4)
  setuptools (11.0)
  simplejson (3.6.5)
  six (1.9.0)
  stevedore (1.2.0)
  uritemplate (0.6)
  urllib3 (1.10)
  virtualenv (12.0.7)
  virtualenv-clone (0.2.5)
  virtualenvwrapper (4.3.2)
  </code></pre>
  
  <p>Any ideas?</p>