lda driver: add error message when no device found

fallen · fallen · commit df232f540573 · 2015-07-07T15:18:28.000+02:00
diff --git a/artiq/devices/lda/driver.py b/artiq/devices/lda/driver.py
@@ -110,7 +110,7 @@ def __init__(self, serial=None, product="LDA-102"):
                                          self._product_ids[self.product],
                                          self.serial)
         if not self._dev:
-            raise IOError
+            raise IOError("Device not found")
 
     def close(self):
         """Close the device."""
