docs: def copy_and_replace(file_in, file_out, mapping, **kwargs):
      '''
      Copy a file and replace some placeholders with new values.
      '''
      separator = '@@'
      if 'separator' in kwargs:
          separator = kwargs['separator']
      file_in = open(file_in, 'r')
      file_out = open(file_out, 'w')
      s = file_in.read()
      for find, replace in mapping:
          find = separator + find + separator
          print(u'Replacing {0} with {1}'.format(find, replace))
          s = s.replace(find, replace)
      file_out.write(s)