docs: Update Makefile to python 3

Author: tony

docs/Makefile

@@ -2,7 +2,6 @@
 #
 WATCH_FILES= find .. -type f -not -path '*/\.*' | grep -i '.*[.]rst\$\|.*[.].md\|.*[.]py\$\|CHANGES\|TODO\|.*conf\.py' 2> /dev/null
 SHELL := /bin/bash
-PYVERSION=$(shell python -c "import sys;v=sys.version_info[0];sys.stdout.write(str(v))")
 HTTP_PORT     = 8031
 
 # You can set these variables from the command line.
@@ -169,10 +168,7 @@ serve:
 	@echo 'docs server running at http://localhost:${HTTP_PORT}/'
 	@echo
 	@echo '=============================================================='
-	@if test ${PYVERSION} -eq 2; then $(MAKE) serve_py2; else make serve_py3; fi
-
-serve_py2:
-	pushd _build/html; python2 -m SimpleHTTPServer ${HTTP_PORT}; popd
+	@$(MAKE) serve_py3
 
 serve_py3:
 	python -m http.server ${HTTP_PORT} --directory _build/html