~$ cd src/numcodecs/docs

~/src/numcodecs/docs$ make
Makefile:12: *** recipe commences before first target.  Stop.

~/src/numcodecs/docs$ make html
Makefile:12: *** recipe commences before first target.  Stop.

~$ cd src/numcodecs/docs

~/src/numcodecs/docs$ make
Makefile:14: *** The 'sphinx-build' command was not found. Make sure you have Sphinx installed, then set the SPHINXBUILD environment variable to point to the full path of the 'sphinx-build' executable. Alternatively you can add the directory with the executable to your PATH. If you don\'t have Sphinx installed, grab it from http://sphinx-doc.org/.  Stop.

~/src/numcodecs/docs$ make html
Makefile:14: *** The 'sphinx-build' command was not found. Make sure you have Sphinx installed, then set the SPHINXBUILD environment variable to point to the full path of the 'sphinx-build' executable. Alternatively you can add the directory with the executable to your PATH. If you don\'t have Sphinx installed, grab it from http://sphinx-doc.org/.  Stop.