fixup! fixup! build: add YAML linting

Makefile

@@ -1410,19 +1410,16 @@ endif
 .PHONY: lint-yaml-build
 # python -m pip install yamllint
 # Try with '--system' if it fails without; the system may have set '--user'
-# Jenkins CI lint job uses python2 for linting. When Node.js 12.x is EOL, we
-# can remove that from the Jenkins job config and $(PYTHON) for YAML linting
-# just like everywhere else. (yamllint does not support Python 2.)
 lint-yaml-build:
 	$(info Pip installing yamllint on $(shell $(PYTHON) --version)...)
-	python3 -m pip install --upgrade -t tools/pip/site-packages yamllint || \
-		python3 -m pip install --upgrade --system -t tools/pip/site-packages yamllint
+	$(PYTHON) -m pip install --upgrade -t tools/pip/site-packages yamllint || \
+		$(PYTHON) -m pip install --upgrade --system -t tools/pip/site-packages yamllint
 
 .PHONY: lint-yaml
 # Lints the YAML files with yamllint.
 lint-yaml:
 	@if [ -f "tools/pip/site-packages/yamllint" ]; then \
-			PYTHONPATH=tools/pip python3 -m yamllint .; \
+			PYTHONPATH=tools/pip $(PYTHON) -m yamllint .; \
 	else \
 		$(warning YAML linting with yamllint is not available) \
 		$(warning Run 'make lint-yaml-build') \