code: def _process_pth(path, base, file_name):
      
      
      pth_path = os.path.abspath(os.path.join(base, file_name))
      
      # This is for `exec` below, as some packages (e.g. virtualenvwrapper)
      # assume that `site.addpackage` is running them.
      sitedir = os.path.dirname(base)
  
      # Only process this once.
      if pth_path in _processed_pths:
          return
      _processed_pths.add(pth_path)    
      
      log.log(1, '_process_pth(..., %r, %r)', base, file_name)
      
      try:
          fh = open(pth_path)
      except IOError as e:
          log.log(1, '_process_path IOError %s' % e)
          return
      
      for line in open(pth_path):
          line = line.strip()
          
          # Blanks and comments.
          if not line or line.startswith('#'):
              continue
          
          # Execs.
          if line.startswith('import'):
              
              # Sorry easy-install: you break our environment.
              if file_name == 'easy-install.pth' and 'sys.__plen' in line:
                  continue
  
              log.log(1, '_process_pth exec %s' % line)
              exec line
              continue
          
          # Replace "{platform_spec}" to allow per-platform paths.
          line = line.format(
              platform_spec=basic_platform_spec,
              basic_platform_spec=basic_platform_spec,
              extended_platform_spec=extended_platform_spec,
          )
  
          path.add(os.path.join(base, line))
docs: Process a ``.pth`` file similar to site.addpackage(...).