title: Custom pip.conf location for pip 8.1
body: <p>I manage a group of Ubuntu 16.04 servers with Python 3.5 and pip 8.1.1 as part of the OS package. The servers do not have access to the Internet and <code>pip</code> needs to be configured with internal pypi mirror. </p>
  
  <p>I have the following config file at <code>/home/hanxue/.config/pip/pip.conf</code></p>
  
  <pre><code>[global]
  index-url = https://pypimirror/simple
  cert = /etc/ssl/certs/ca-certificates.crt
  </code></pre>
  
  <p>Unfortunately pip 8.1.1 does not read the config file located at <code>~/.config/pip/pip.conf</code>. Only pip version >10 and above use the more consistent XDG path at <code>~/.config/pip/pip.conf</code></p>
  
  <p>I have tried setting the <code>PIP_CONFIG_FILE</code> environment variable but pip 8.1.1 is not picking it up</p>
  
  <pre><code>$ PIP_CONFIG_FILE=/home/hanxue/.config/pip/pip.conf /usr/bin/pip3 search tensorflow
  </code></pre>
  
  <p>I know I can just create a copy of the file at <code>~/.pip/pip.conf</code> to solve the problem. But this is for the end users, and they will end up with 2 <code>pip.conf</code>  and thus generating confusion down the road. For example, editing <code>~/.pip/pip.conf</code> but found out that pip 19 / python 3.6 does not pick up the settings. </p>
  
  <p>How can I get pip 8.1 to pick up the config from a non-standard location?</p>