title: Python OpenAI Atari module in Ubuntu 16.04 - "No module named atari_py."
body: <p>(I'm new to Ubuntu, excuse any ignorance.)  I'm trying to run SpaceInvaders in Python using OpenAI's Atari module, however I keep getting the error </p>
  
  <blockquote>
    <p>File
    "/usr/local/lib/python2.7/dist-packages/gym/envs/atari/atari_env.py",
    line 11, in  raise error.DependencyNotInstalled("{}. (HINT:
    you can install Atari dependencies by running 'pip install
    gym[atari]'.)".format(e))gym.error.DependencyNotInstalled: No module
    named atari_py. (HINT: you can install Atari dependencies by running
    'pip install gym[atari]'.)</p>
  </blockquote>
  
  <p>The command suggested in the error is exactly what I used to install gym.  I've read in <a href="https://stackoverflow.com/questions/35103338/python-no-module-named-how-to-use-pip">another forum</a> that this means not all the dependencies are loaded, so I've taken great care to download this dependencies listed <a href="https://github.com/openai/gym/blob/master/README.rst" rel="nofollow noreferrer">here</a>.  Here's some proof that they're properly installed: </p>
  
  <pre><code>$ dpkg -s python-numpy python-dev cmake zlib1g-dev libjpeg-dev xvfb libav-tools xorg-dev python-opengl libboost-all-dev libsdl2-dev swig | grep  Status
  Status: install ok installed
  Status: install ok installed
  Status: install ok installed
  Status: install ok installed
  Status: install ok installed
  Status: install ok installed
  Status: install ok installed
  Status: install ok installed
  Status: install ok installed
  Status: install ok installed
  Status: install ok installed
  Status: install ok installed
  </code></pre>
  
  <p>Is there anything else I should be aware of, or another way I can be troubleshooting this issue?</p>