title: Deploying app with heroku and docker throws error when installing requirements
body: <p>Hi I want to deploy a <code>dash app</code> that makes use of <code>scikit-learn</code> and <code>xgboost</code>. According to Heroku's <a href="https://help.heroku.com/S48C2M3H/can-i-use-scientific-python-libraries-scipy-scikit-learn-etc-on-heroku" rel="nofollow noreferrer">documentation</a> this should be possible using docker. I am following their approach as suggested on <a href="https://github.com/heroku-examples/python-miniconda" rel="nofollow noreferrer">github</a>.</p>
  
  <p>However, I receive an error after running the last step to deploy my app <code>heroku container:push web</code>.</p>
  
  <pre><code>(Project) C:\Users\Project\venv&gt;heroku container:push web
  === Building web (C:\Users\Project\venv\Dockerfile)
  Sending build context to Docker daemon  917.5kB
  Step 1/7 : FROM heroku/miniconda
   ---&gt; 8b1058516fe3
  Step 2/7 : ADD ./webapp/requirements.txt /tmp/requirements.txt
   ---&gt; a3190f679660
  Step 3/7 : RUN pip install -qr /tmp/requirements.txt
   ---&gt; Running in 2e0f82c37221
  Command "python setup.py egg_info" failed with error code 1 in /tmp/pip-build-XjwVjo/matplotlib/
  The command '/bin/sh -c pip install -qr /tmp/requirements.txt' returned a non-zero code: 1
   !    Error: docker build exited with Error: 1
  </code></pre>
  
  <p>My folder structure looks as follows:</p>
  
  <pre><code>venv/
     Dockerfile
     webapp/
         assets/
            style.css
         .gitignore
         data.csv
         Main.py --&gt; Dash App
         models.py
         prepareDataSet.py
         requirements.txt
         wsgi.py
  </code></pre>
  
  <p>I am using <code>python 3.6.1</code>, <code>pip 19.3.1</code> &amp; <code>setuptools 45.1.0</code></p>
  
  <p>IDK if this is helpful - my Dockerfile looks like:</p>
  
  <pre><code>FROM heroku/miniconda
  
  # Grab requirements.txt.
  ADD ./webapp/requirements.txt /tmp/requirements.txt
  
  # Install dependencies
  RUN pip install -qr /tmp/requirements.txt
  
  # Add our code
  ADD ./webapp /opt/webapp/
  WORKDIR /opt/webapp
  
  RUN conda install scikit-learn xgboost
  
  CMD gunicorn --bind 0.0.0.0:$PORT wsgi
  </code></pre>
  
  <p>Help much appreciated!</p>