add preprocessing to ThreadedButton

gui/qt/util.py

@@ -73,8 +73,9 @@ class EnterButton(QPushButton):
 
 
 class ThreadedButton(QPushButton):
-    def __init__(self, text, func, on_success=None):
+    def __init__(self, text, func, on_success=None, before=None):
         QPushButton.__init__(self, text)
+        self.before = before
         self.run_task = func
         self.on_success = on_success
         self.clicked.connect(self.do_exec)
@@ -95,12 +96,15 @@ class ThreadedButton(QPushButton):
         try:
             self.result = self.run_task()
         except BaseException as e:
+            traceback.print_exc(file=sys.stdout)
             self.error = str(e.message)
             self.emit(SIGNAL('error'))
             return
         self.emit(SIGNAL('done'))
 
     def do_exec(self):
+        if self.before:
+            self.before()
         t = threading.Thread(target=self.do_func)
         t.setDaemon(True)
         t.start()