configure: Add checking python3-sphinx
This is a continuation of !1989 (closed).
This checks the configuration about python3-sphinx. We need python3-sphinx instead of python2-sphinx to build documentation.
The approach is as follows:
- Check python3 version with custom
conf.py
invoked fromsphinx-build
executable - Place custom
conf.py
into newutils/check-sphinx
directory
If sphinx is for python2 not python3, it's treated as config ERROR instead of WARN.
See also #17346 (closed) and #17356 (closed).