Add RefreshError workaround

src/main/python/main.py

@@ -6,6 +6,7 @@
 from google.auth.transport.requests import Request
 from spreadsheet_handler import SpreadsheetHandler
 from widget_gallery import WidgetGallery
+import google.auth.exceptions as GoogleExceptions
 from fbs_runtime.application_context.PyQt5 import ApplicationContext
 from PyQt5.QtWidgets import QApplication, QMessageBox
 from PyQt5.QtGui import QIcon, QFont
@@ -59,9 +60,27 @@
     # If there are no (valid) credentials available, let the user log in.
     if not CREDS or not CREDS.valid:
         if CREDS and CREDS.expired and CREDS.refresh_token:
-            CREDS.refresh(Request())
+            try:
+                CREDS.refresh(Request())
+            except GoogleExceptions.RefreshError:
+                error_message = "Your access token has expired. Please, complete the authentication flow once again, " + \
+                                "accessing your google account on the website" + \
+                                " that will be opened when you close this window."
+                print(error_message)
+                app = QApplication([])
+                error_window = QMessageBox()
+                error_window.setWindowTitle("Expenses Tracker")
+                error_window.setWindowIcon(QIcon(ApplicationContext().get_resource("submit.ico")))
+                error_window.setIcon(QMessageBox.Critical)
+                error_window.setText(error_message)
+                error_window.setStandardButtons(QMessageBox.Ok)
+                error_window.setDefaultButton(QMessageBox.Ok)
+                error_window.exec_()
+
+                flow = InstalledAppFlow.from_client_secrets_file('credentials.json', SCOPES)
+                CREDS = flow.run_local_server(port=0)
         else:
-            error_message = "Please complete the authentication flow " + \
+            error_message = "Please, complete the authentication flow " + \
                             "accessing your google account on the website" + \
                             " that will be opened when you close this window."
             print(error_message)