build(docs,Makefile): Python 3 only

Author: tony

docs/Makefile

@@ -170,13 +170,7 @@ 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
-
-serve_py3:
-	python -m http.server ${HTTP_PORT} --directory _build/html
+	poetry run python -m http.server ${HTTP_PORT} --directory _build/html
 
 dev:
 	$(MAKE) -j watch serve