docs: def run_pip_install(upgrade=0):
      """
      Installs the requirement.txt file on the given server.
  
      Usage::
  
          fab <server> run_pip_install
          fab <server> run_pip_install:upgrade=1
  
      :param upgrade: If set to 1, the command will be executed with the
        ``--upgrade`` flag.
  
      """
      command = 'pip install -r {0}'.format(
          settings.FAB_SETTING('SERVER_REQUIREMENTS_PATH'))
      if upgrade:
          command += ' --upgrade'
      run_workon(command)