title: Docker image error: "/bin/sh: 1: [python,: not found"
body: <p>I'm building a new Docker image based on the standard Ubuntu 14.04 image. </p>
  
  <p>Here's my <em>Dockerfile</em>:</p>
  
  <pre><code>FROM ubuntu:14.04
  RUN apt-get update -y
  RUN apt-get install -y nginx git python-setuptools python-dev
  RUN easy_install pip
  ADD . /code
  WORKDIR /code
  RUN pip install -r requirements.txt # only 'django' for now
  ENV projectname myproject
  EXPOSE 80 8000
  WORKDIR ${projectname}
  CMD ['python', 'manage.py', 'runserver', '0.0.0.0:80']
  </code></pre>
  
  <p>When I try to run this image, I get this error...</p>
  
  <blockquote>
    <p>/bin/sh: 1: [python,: not found</p>
  </blockquote>
  
  <p>But if I open a shell when running the image, running <code>python</code> opens the interactive prompt as expected. </p>
  
  <p>Why can't I invoke <code>python</code> through <code>CMD</code> in the Dockerfile?</p>