Run a subcommand, quietly.  Prints the full command on error.

def _run_command(self, cmdline):
        """Run a subcommand, quietly.  Prints the full command on error."""
        try:
            if self.verbose:
                print(cmdline)
            subprocess.check_call(cmdline, shell=True)
        except subprocess.CalledProcessError:
            print('when running: ', cmdline)
            raise