old_contents: __all__ = ['__version__']
  import pkg_resources
  
  try:
      __version__ = pkg_resources.get_distribution('pytest').version
  except Exception:
      __version__ = None  # broken installation, we don't even try
  
new_contents: import pkg_resources
  
  __all__ = ['__version__']
  
  try:
      __version__ = pkg_resources.get_distribution('pytest').version
  except Exception:
      # broken installation, we don't even try
      # unknown only works because we do poor mans version compare
      __version__ = 'unknown'
  
subject: use unknown to specify unknown versions