title: flake8 module installed but not un /usr/bin
body: <p>I have installed flake8 successfully:</p>
  
  <pre><code>$ pip install flake8
  Downloading/unpacking flake8
    Downloading flake8-2.5.4-py2.py3-none-any.whl
  Downloading/unpacking mccabe&lt;0.5,&gt;=0.2.1 (from flake8)
    Downloading mccabe-0.4.0-py2.py3-none-any.whl
  Downloading/unpacking pep8!=1.6.0,!=1.6.1,!=1.6.2,&gt;=1.5.7 (from flake8)
    Downloading pep8-1.7.0-py2.py3-none-any.whl (41kB): 41kB downloaded
  Downloading/unpacking pyflakes&lt;1.1,&gt;=0.8.1 (from flake8)
    Downloading pyflakes-1.0.0-py2.py3-none-any.whl (152kB): 152kB downloaded
  Installing collected packages: flake8, mccabe, pep8, pyflakes
  Successfully installed flake8 mccabe pep8 pyflakes
  Cleaning up...
  
  $ pip list|grep flake
  flake8 (2.5.4)
  pyflakes (1.0.0)
  </code></pre>
  
  <p>But it doesn't appear in any of the directories under /usr (/usr/bin/, /usr/sbin/, /usr/local/...) i.e. "which flake8" doesn't show anything, so I can't use from the console manually to verify a script like in the instructions.</p>