Update machine state on unhandled exceptions

news.d/bugfix/1560.ui.md

@@ -0,0 +1 @@
+Update the tray icon to "disconnected" when a serial-over-USB machine is unplugged.

plover/machine/base.py

@@ -149,10 +149,18 @@ class ThreadedStenotypeBase(StenotypeBase, threading.Thread):
     """
     def __init__(self):
         threading.Thread.__init__(self)
+        self._on_unhandled_exception(self._error)
         self.name += '-machine'
         StenotypeBase.__init__(self)
         self.finished = threading.Event()
 
+    def _on_unhandled_exception(self, action):
+        super_invoke_excepthook = self._invoke_excepthook
+        def invoke_excepthook(self):
+            action()
+            super_invoke_excepthook(self)
+        self._invoke_excepthook = invoke_excepthook
+
     def run(self):
         """This method should be overridden by a subclass."""
         pass

test/test_machine.py

@@ -0,0 +1,14 @@
+from unittest.mock import Mock
+from plover.machine.base import ThreadedStenotypeBase
+
+class MyMachine(ThreadedStenotypeBase):
+    def run(self):
+        raise "some unexpected error"
+
+def test_update_machine_staten_on_unhandled_exception():
+    machine = MyMachine()
+    callback = Mock()
+    machine.add_state_callback(callback)
+    machine.start_capture()
+    machine.join()
+    callback.assert_called_with('disconnected')