Python 2 is going to be removed from Debian at some point, so
build-depend on Python 3 packages instead. Fixes Lintian Warning:
build-depends-on-python-sphinx-only
Change-Id: Id17189a91436d776ce35a4c73ed746abc968f74f
Signed-off-by: Luca Boccassi <luca.boccassi@gmail.com>
(cherry picked from commit
b86ee01f5e76435ea128bdb84b97c8809da0ae09)
Signed-off-by: Luca Boccassi <luca.boccassi@gmail.com>