sudo apt-get install python3-sphinx

sudo apt-get remove python-sphinx

#!/usr/bin/python3
# -*- coding: utf-8 -*-
"""
Same as /usr/bin/sphinx-build but with different
interpreter
"""

import sys

if __name__ == '__main__':
    from sphinx import main, make_main
    if sys.argv[1:2] == ['-M']:
        sys.exit(make_main(sys.argv))
    else:
        sys.exit(main(sys.argv))

SPHINXBUILD   = sphinx3-build

sudo cp sphinx3-build /usr/bin/

SPHINXBUILD   = python3 -c "import sys,sphinx;sys.exit(sphinx.main(sys.argv))"

SPHINXBUILD   = python -msphinx