Add a user

def marvcli_user_add(ctx, username, password):
    """Add a user"""
    if not re.match(r'[0-9a-zA-Z\-_\.@+]+$', username):
        click.echo('Invalid username: {}'.format(username), err=True)
        click.echo('Must only contain ASCII letters, numbers, dash, underscore and dot',
                   err=True)
        sys.exit(1)
    if password is None:
        password = click.prompt('Password', hide_input=True, confirmation_prompt=True)
    app = create_app()
    try:
        app.um.user_add(username, password, 'marv', '')
    except ValueError as e:
        click.echo('Error: {}'.format(e.args[0], err=True))
        sys.exit(1)