Create output from Jinja template.

def gen_text(env: TextIOBase, package: str, tmpl: str):
    """Create output from Jinja template."""
    if env:
        env_args = json_datetime.load(env)
    else:
        env_args = {}
    jinja_env = template.setup(package)
    echo(jinja_env.get_template(tmpl).render(**env_args))