Safety checks for required apps.

lib/python/qmk/cli/generate/docs.py

@@ -1,5 +1,6 @@
 """Build QMK documentation locally
 """
+import shutil
 from qmk.docs import prepare_docs_build_area, run_docs_command, BUILD_DOCS_PATH
 
 from milc import cli
@@ -14,6 +15,14 @@ def generate_docs(cli):
         * [ ] Add a real build step... something static docs
     """
 
+    if not shutil.which('doxygen'):
+        cli.log.error('doxygen is not installed. Please install it and try again.')
+        return
+
+    if not shutil.which('npm'):
+        cli.log.error('npm is not installed. Please install it and try again.')
+        return
+
     prepare_docs_build_area()
 
     cli.log.info('Building docusaurus docs')