Return new Command object that will be run with a new addition
        to the PATH environment variable that will be fed to the command.

def with_path(self, path):
        """
        Return new Command object that will be run with a new addition
        to the PATH environment variable that will be fed to the command.
        """
        new_command = copy.deepcopy(self)
        new_command._paths.append(str(path))
        return new_command