title: Docker build fails on RUN pip install -e git <repo url>
body: <p>I am trying to build a docker image.</p>
  
  <pre><code>This is my docker file
  FROM python:3.6
  RUN apt-get -y update
  RUN apt-get install -y gcc libc-dev g++ libffi-dev libxml2 libffi-dev unixodbc-dev default-libmysqlclient-dev
  COPY requirements.txt requirements.txt
  RUN pip install numpy
  RUN pip install -e git+&lt;git repo&gt;
  RUN pip install -r requirements.txt
  </code></pre>
  
  <p>But the RUN pip install -e git+ fails. I tweaked my dns setting in the docker.service file, but still no luck.</p>