add a function to display an error dialog

borg_qt/helper.py

@@ -1,2 +1,15 @@
+from PyQt5.QtWidgets import QMessageBox
+
+
 class BorgException(Exception):
     pass
+
+
+def show_error(e):
+    # Error Dialog
+    message = QMessageBox()
+    message.setIcon(QMessageBox.Warning)
+    message.setText("Error")
+    message.setWindowTitle("Borg-Qt Error")
+    message.setInformativeText(e.args[0])
+    message.exec_()