update to vent, add validation

Makefile

@@ -1,7 +1,22 @@
 .PHONY: env
 
+VNU_RELEASE=20.6.30
+VNU_URL=https://github.com/validator/validator/releases/download/$(VNU_RELEASE)/vnu.jar_$(VNU_RELEASE).zip
+
+vnu.jar_$(VNU_RELEASE).zip:
+	wget $(VNU_URL)
+
+vnu.jar: vnu.jar_$(VNU_RELEASE).zip
+	unzip -p $< dist/vnu.jar > $@ || (rm "$@"; false)
+
+.PHONY: validate
+validate: vnu.jar
+	hyde gen
+	java -jar vnu.jar --also-check-css --stdout $$(find deploy -name '*.html' -o -name '*.css') | egrep -v 'Section lacks heading|Article lacks heading|Consider using the “h1” element as a top-level heading only' || true
+	#java -jar vnu.jar --svg --stdout $$(find deploy -name '*.svg') | egrep -v 'The value of attribute “unicode” on element “glyph” from namespace “http://www.w3.org/2000/svg” is not in Unicode Normalization Form C.' || true
+
 env:
-	(virtualenv p && . ./p/bin/activate && pip install -r requirements.txt)
+	(python3 -m venv p && . ./p/bin/activate && pip install -r requirements.txt)
 
 .PHONY: deploy