$ sphinx-autogen example.py
[autosummary] example.py の autosummary を生成中
Traceback (most recent call last):
  File "/Users/tkomiya/work/tmp/bin/sphinx-autogen", line 11, in <module>
    load_entry_point('Sphinx', 'console_scripts', 'sphinx-autogen')()
  File "/Users/tkomiya/work/sphinx/sphinx/ext/autosummary/generate.py", line 517, in main
    generate_autosummary_docs(args.source_file, args.output_dir,
  File "/Users/tkomiya/work/sphinx/sphinx/ext/autosummary/generate.py", line 304, in generate_autosummary_docs
    content = generate_autosummary_content(name, obj, parent, template, entry.template,
  File "/Users/tkomiya/work/sphinx/sphinx/ext/autosummary/generate.py", line 245, in generate_autosummary_content
    return template.render(template_name, ns)
  File "/Users/tkomiya/work/sphinx/sphinx/ext/autosummary/generate.py", line 144, in render
    return self.env.get_template(template_name).render(context)
  File "/Users/tkomiya/.pyenv/versions/3.8.1/lib/python3.8/site-packages/Jinja2-3.0.0a1-py3.8.egg/jinja2/environment.py", line 1045, in render
    self.environment.handle_exception()
  File "/Users/tkomiya/.pyenv/versions/3.8.1/lib/python3.8/site-packages/Jinja2-3.0.0a1-py3.8.egg/jinja2/environment.py", line 787, in handle_exception
    raise rewrite_traceback_stack(source=source)
  File "/Users/tkomiya/work/sphinx/sphinx/ext/autosummary/templates/autosummary/module.rst", line 5, in top-level template code
    {% block functions %}
  File "/Users/tkomiya/work/sphinx/sphinx/ext/autosummary/templates/autosummary/module.rst", line 7, in block 'functions'
    .. rubric:: {{ _('Functions') }}
  File "/Users/tkomiya/.pyenv/versions/3.8.1/lib/python3.8/site-packages/Jinja2-3.0.0a1-py3.8.egg/jinja2/sandbox.py", line 410, in call
    if not __self.is_safe_callable(__obj):
  File "/Users/tkomiya/.pyenv/versions/3.8.1/lib/python3.8/site-packages/Jinja2-3.0.0a1-py3.8.egg/jinja2/sandbox.py", line 310, in is_safe_callable
    getattr(obj, "unsafe_callable", False) or getattr(obj, "alters_data", False)
jinja2.exceptions.UndefinedError: '_' is undefined