old_contents: #! /usr/local/bin/python3
  # can not be used on windows due to line end difference.
  import pip
  from subprocess import call
  
  for dist in pip.get_installed_distributions():
      call("pip3 install --upgrade --no-cache-dir" + dist.project_name, shell=True)
  
new_contents: #! /usr/local/bin/python3
  # can not be used on windows due to line end difference.
  import pip
  from subprocess import call
  
  for dist in pip.get_installed_distributions():
      call("pip3 install --upgrade --no-cache-dir " + dist.project_name, shell=True)
  
subject: fix bug