distutils_enable_sphinx acts weird when there is only one python
version in PYTHON_COMPAT, for some reason it wants to add
PYTHON_SINGLE_TARGET to use of sphinx-* deps, but these deps
don't have PYTHON_SINGLE_TARGET
Package-Manager: Portage-2.3.88, Repoman-2.3.20
Signed-off-by: Andrew Ammerlaan <andrewammerlaan@riseup.net>