Navigation broken about docs

[probonopd]

With

github_doc_root = 'https://' + os.environ['GITHUB_REPOSITORY'].split("/")[0] + '.github.io/' + os.environ['GITHUB_REPOSITORY'].split("/")[1] + '/'
def setup(app):
    app.add_config_value('recommonmark_config', {
            'enable_auto_toc_tree': True,
            'url_resolver': lambda url: github_doc_root + url,
            'auto_toc_tree_section': 'Contents',
            }, True)
    app.add_transform(AutoStructify)

the following works:

## Contents

* [hello](index.md)
* [Acknowledgements](acknowledgements.md)

Documentation issue?