title: Heroku + gunicorn not working (bash: gunicorn: command not found )
body: <p>I successfully install gunicorn:</p>
  
  <pre><code>remote: -----&gt; Removing .DS_Store files
  remote: -----&gt; Python app detected
  remote: -----&gt; Installing dependencies with pip
  remote:        Collecting gunicorn==19.0.0 (from -r requirements.txt (line 1))
  remote:          Downloading gunicorn-19.0.0.tar.gz (382kB)
  remote:        Installing collected packages: gunicorn
  remote:          Running setup.py install for gunicorn
  remote:        Successfully installed gunicorn-19.0.0
  </code></pre>
  
  <p>My Procfile:</p>
  
  <pre><code>web: gunicorn myapp:app --log-file=-
  </code></pre>
  
  <p>But the app crashes when deployed:</p>
  
  <pre><code>bash: gunicorn: command not found 
  </code></pre>
  
  <p>I tried adding the heroku python buildpack, but no luck. If I roll back to a previous commit (where <code>requirements.txt</code> and <code>Procile</code> are both unchanged), it works:</p>
  
  <pre><code>heroku/web.1:  Starting process with command `gunicorn myapp:app --log-file=-` 
  app/web.1:  2015-10-08 17:04:18 [3] [INFO] Listening at: http://0.0.0.0:51854 (3)
  </code></pre>