On a sphinx-free Ubuntu system with 4.10-rc5, make installmandocs works just fine, but the garrulous Makefile.sphinx twice tells me I don't have sphinx-build installed:
Documentation/Makefile.sphinx:22: The 'sphinx-build' command was not found. Make sure you have Sphinx installed and in PATH, or set the SPHINXBUILD make variable to point to the full path of the 'sphinx-build' executable. SKIP Sphinx include/config/auto.conf target. Documentation/Makefile.sphinx:22: The 'sphinx-build' command was not found. Make sure you have Sphinx installed and in PATH, or set the SPHINXBUILD make variable to point to the full path of the 'sphinx-build' executable. SKIP Sphinx installmandocs target. Would the 'SKIP ...' statements suffice? It happens with make cleandocs and make mandocs too. -- Jim