re-initialize io.usb if previous failed

Author: rickwierenga

pylabrobot/io/usb.py

@@ -296,16 +296,18 @@ def ctrl_transfer(
   async def setup(self):
     """Initialize the USB connection to the machine."""
 
+    if self.dev is not None:
+      # previous setup did not properly finish,
+      # or we are re-initializing the device.
+      logger.warning("USB device already connected. Closing previous connection.")
+      await self.stop()
+
     if not USE_USB:
       raise RuntimeError(
         "USB is not enabled. Please install pyusb and libusb. "
         "https://docs.pylabrobot.org/installation.html"
       )
 
-    if self.dev is not None:
-      logging.warning("Already initialized. Please call stop() first.")
-      return
-
     logger.info("Finding USB device...")
 
     devices = self.get_available_devices()