At first, thank you very much for providing this handy tool!
Just recently (yesterday evening and this morning), I got the mentioned error messages. The related commands were:
if [ $TRAVIS_PYTHON_VERSION = "2.7" ] ; then travis-sphinx --source=hydpy/docs build; fi
if [ $TRAVIS_PYTHON_VERSION = "2.7" ] ; then python modify_html.py; fi
See the following link for more information: https://github.com/tyralla/hydpy/blob/develop/.travis.yml
Maybe this problem is related with issue #28?
Please let me know if further information is required.
Best regards,
Christoph.