title: How python36 initialise PYTHONPATH?
body: <p>Two newly installed from the same scratch VMs with the same python36 versions have different values for sys.path:</p>
  
  <p>1st VM</p>
  
  <pre><code>[root@vm1 ~]# python36 -m site
  sys.path = [
      '/root',
      '/usr/lib64/python36.zip',
      '/usr/lib64/python3.6',
      '/usr/lib64/python3.6/lib-dynload',
      '/usr/lib64/python3.6/site-packages',
      '/usr/lib/python3.6/site-packages',
  ]
  USER_BASE: '/root/.local' (doesn't exist)
  USER_SITE: '/root/.local/lib/python3.6/site-packages' (doesn't exist)
  ENABLE_USER_SITE: True
  </code></pre>
  
  <p>2nd VM</p>
  
  <pre><code>[root@vm2 ~]# python36 -m site
  sys.path = [
      '/root',
      '/usr/lib64/python36.zip',
      '/usr/lib64/python3.6',
      '/usr/lib64/python3.6/lib-dynload',
      '/usr/local/lib64/python3.6/site-packages',
      '/usr/local/lib/python3.6/site-packages',
      '/usr/lib64/python3.6/site-packages',
      '/usr/lib/python3.6/site-packages',
  ]
  USER_BASE: '/root/.local' (doesn't exist)
  USER_SITE: '/root/.local/lib/python3.6/site-packages' (doesn't exist)
  ENABLE_USER_SITE: True
  </code></pre>
  
  <p>2nd VM has /usr/local/lib* paths for some reasons. </p>
  
  <p>os.environ on both machines shows the same values for variables:</p>
  
  <ul>
  <li>no custom path values for PYTHONPATH</li>
  <li><p>original PATH variables(dunno if they are connected to PYTHONPATH)
  are also the same</p>
  
  <p>[root@vm1 ~] env | grep -E "^PATH="
  PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/opt/java/latest/bin:/opt/java/latest/jre/bin:/root/bin</p></li>
  </ul>
  
  <p>How python36 initialise PYTHONPATH(sys.path) during initial installation, when no custom values at OS side for PYTHONPATH are configured?</p>