fix(make): use venv-python to run any utility

Previously the yaml version generation could fail if your system-python
didn't have yaml installed. Now the virtual env is used, which is
guaranteed to support yaml.

src/mako/deps.mako

@@ -188,5 +188,5 @@ ${fake_target}:
 % endfor
 
 update-json: ${' '.join(json_api_targets)}
-	$(API_VERSION_GEN) $(API_DIR) $(API_LIST) $(API_LIST)
+	$(PYTHON) $(API_VERSION_GEN) $(API_DIR) $(API_LIST) $(API_LIST)
 % endif