[engine] Report current module when error occurs

Keep track of the latest updated module in the engine part, so that the
module causing an exception can be reported correctly.

fixes #110

bumblebee-status

@@ -42,6 +42,7 @@ def main():
         inp.stop()
         sys.exit(0)
     except BaseException as e:
+        module = engine.current_module()
         logging.exception(e)
         if output.started():
             output.flush()
@@ -52,7 +53,7 @@ def main():
         while True:
             output.begin()
             error = bumblebee.modules.error.Module(engine, config)
-            error.set("exception occurred: {}".format(e))
+            error.set("exception occurred: {} in {}".format(e, module))
             widget = error.widgets()[0]
             widget.link_module(error)
             output.draw(widget, error)