/usr/share/sphinx/themes/epub/theme.conf is in sphinx-common 1.3.6-2ubuntu1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 | [theme]
inherit = basic
stylesheet = epub.css
pygments_style = none
[options]
relbar1 = true
footer = true
|