docs: def exec(self, *command_tokens, **command_env):
  		""" :meth:`.WCommandProto.exec` implementation
  
  		(throws RuntimeError if tokens are invalid, and calls :meth:`.WCommand._exec` method)
  		"""
  		if self.match(*command_tokens, **command_env) is False:
  			raise RuntimeError('Command mismatch: %s' % self.join_tokens(*command_tokens))
  
  		return self._exec(*command_tokens, **command_env)