Django - unsupported format character 'a' (0x61)

I was receiving the following error

unsupported format character 'a' (0x61) at index 16

def send_notification_email(sender, **kwargs):
    change = sender
    print "=========================================="
    mail_admins(subject="model %(model) has been changed by %(user)" % 
                            {'开发者_开发问答model':change.content_type, 'user': change.user},
                message = render_to_string('change_email.html', { 'change': change }) )

Any suggestions?

You forgot the format specifier.

%(model)s