title: I can't install python packages by using pip3 on alpine
body: <p>Could not install packages due to an EnvironmentError: [Errno 39] Directory not empty: '/tmp/pip-install-xo15v1tw/mock/mock'</p>
  
  <p>I created an alpine container. Dockerfile is</p>
  
  <pre><code>FROM alpine:latest
  </code></pre>
  
  <p>I built and run it.</p>
  
  <pre><code>#sudo docker build -t alpine .
  #sudo docker run -it alpine
  
  </code></pre>
  
  <p>Then, I installed python3</p>
  
  <pre><code>#apk add python3
  </code></pre>
  
  <p>Then, I tried to install mock package and I got error.</p>
  
  <pre><code>#pip3 install mock
  ...
  Could not install packages due to an EnvironmentError: [Errno 39] Directory not empty: '/tmp/pip-install-xo15v1tw/mock/mock'
  </code></pre>
  
  <p>I tried to install other python packages, but I always got the same error.
  I'm running on the container on WSL. The version of alpine is 3.9.4.</p>
  
  <p>How do I solve this problem?</p>