title: Can't install python module with Dockerfile
body: <p>I am unable to install Flask-User from my requirements file as when it comes to that module I get the error:</p>
  
  <pre><code>Collecting bcrypt&gt;=2.0 (from flask-user-&gt;-r requirements.txt (line 8))
    Downloading https://files.pythonhosted.org/packages/ce/3a/3d540b9f5ee8d92ce757eebacf167b9deedb8e30aedec69a2a072b2399bb/bcrypt-3.1.6.tar.gz (42kB)
    Installing build dependencies: started
    Installing build dependencies: finished with status 'error'
    Complete output from command /usr/local/bin/python /usr/local/lib/python3.6/site-packages/pip install --ignore-installed --no-user --prefix /tmp/pip-build-env-vtowffrv/overlay --no-warn-script-location --no-binary :none: --only-binary :none: -i https://pypi.org/simple -- setuptools wheel "cffi&gt;=1.1; python_implementation != 'PyPy'":
    Collecting setuptools
      Downloading https://files.pythonhosted.org/packages/82/9c/e812a9838feaf76cd9a960ca4ced3be7f2db31e473677a621d006e128db2/setuptools-40.7.3-py2.py3-none-any.whl (574kB)
    Collecting wheel
      Downloading https://files.pythonhosted.org/packages/ff/47/1dfa4795e24fd6f93d5d58602dd716c3f101cfd5a77cd9acbe519b44a0a9/wheel-0.32.3-py2.py3-none-any.whl
    Collecting cffi&gt;=1.1
      Downloading https://files.pythonhosted.org/packages/e7/a7/4cd50e57cc6f436f1cc3a7e8fa700ff9b8b4d471620629074913e3735fb2/cffi-1.11.5.tar.gz (438kB)
        Complete output from command python setup.py egg_info:
  
            No working compiler found, or bogus compiler options passed to
            the compiler from Python's standard "distutils" module.  See
            the error messages above.  Likely, the problem is not related
            to CFFI but generic to the setup.py of any Python package that
            tries to compile C code.  (Hints: on OS/X 10.8, for errors about
            -mno-fused-madd see http://stackoverflow.com/questions/22313407/
            Otherwise, see https://wiki.python.org/moin/CompLangPython or
            the IRC channel #python on irc.freenode.net.)
  
        ----------------------------------------
    Command "python setup.py egg_info" failed with error code 1 in /tmp/pip-install-wt1ra3xd/cffi/
  
    ----------------------------------------
  Command "/usr/local/bin/python /usr/local/lib/python3.6/site-packages/pip install --ignore-installed --no-user --prefix /tmp/pip-build-env-vtowffrv/overlay --no-warn-script-location --no-binary :none: --only-binary :none: -i https://pypi.org/simple -- setuptools wheel "cffi&gt;=1.1; python_implementation != 'PyPy'"" failed with error code 1 in None
  ERROR: Service 'frontend' failed to build: The command '/bin/sh -c pip install -r requirements.txt' returned a non-zero code: 1
  </code></pre>
  
  <p>I have tried to upgrade pip, and install setuptools to no avail.</p>
  
  <p>This is my dockerfile:</p>
  
  <pre><code>FROM python:3.6-alpine
  WORKDIR /app
  COPY requirements.txt /app
  COPY app.py /app
  COPY templates /app/templates
  RUN pip install -r requirements.txt
  EXPOSE 5000
  ENTRYPOINT ["python"]
  CMD ["app.py"]
  </code></pre>
  
  <p>requirements.txt:</p>
  
  <pre><code>Flask
  requests
  jsonify
  pymongo
  request
  wtforms
  flask-mongoengine
  flask-user
  </code></pre>
  
  <p>Edit:</p>
  
  <p>Appears gcc is not included in the alpine base image.
  I resolved this issue by using <code>FROM python:3.6-slim</code> instead.</p>