Show errorMessage with not existing file to load

labelme/app.py

@@ -738,7 +738,10 @@ class MainWindow(QMainWindow, WindowMixin):
         if filename is None:
             filename = self.settings.get('filename', '')
         filename = str(filename)
-        if QFile.exists(filename):
+        if not QFile.exists(filename):
+            self.errorMessage(
+                'Error opening file', 'No such file: <b>%s</b>' % filename)
+            return False
         # assumes same name, but json extension
         self.status("Loading %s..." % os.path.basename(str(filename)))
         label_file = os.path.splitext(filename)[0] + '.json'
@@ -799,7 +802,6 @@ class MainWindow(QMainWindow, WindowMixin):
         if filename in self.imageList:
             self.fileListWidget.setCurrentRow(self.imageList.index(filename))
         return True
-        return False
 
     def resizeEvent(self, event):
         if self.canvas and not self.image.isNull()\