Exit cleanly on non-RPi picam dry runs

Author: bonnieking

src/ac_training_lab/picam/device.py

@@ -177,6 +177,10 @@ def call_lambda(action, CAM_NAME, WORKFLOW_NAME, privacy_status="private"):
 
     print(f"Streaming to: {ffmpeg_url}")
 
+    if not shutil.which("rpicam-vid") and not shutil.which("libcamera-vid"):
+        print("No Raspberry Pi camera command found; exiting after Lambda dry-run")
+        raise SystemExit(0)
+
     while True:
         print("Starting stream..")
         p1, p2 = start_stream(ffmpeg_url)