Check README for supported models (#684)

* Check README for supported models

* Use poetry for running due to imports

* Update README

devtools/check_readme_vs_fixtures.py

@@ -1,4 +1,6 @@
 """Script that checks if README.md is missing devices that have fixtures."""
+import sys
+
 from kasa.tests.conftest import (
     ALL_DEVICES,
     BULBS,
@@ -28,6 +30,12 @@ def _get_device_type(dev, typemap):
         return "Unknown type"
 
 
+found_unlisted = False
 for dev in ALL_DEVICES:
     if dev not in readme:
         print(f"{dev} not listed in {_get_device_type(dev, typemap)}")
+        found_unlisted = True
+
+
+if found_unlisted:
+    sys.exit(-1)