Fix download for firmware upgrade notification

Same issue as the download for Cura version upgrade in CURA-4464.

plugins/FirmwareUpdateChecker/FirmwareUpdateChecker.py

@@ -1,6 +1,9 @@
 # Copyright (c) 2017 Ultimaker B.V.
 # Cura is released under the terms of the LGPLv3 or higher.
 
+from PyQt5.QtCore import QUrl
+from PyQt5.QtGui import QDesktopServices
+
 from UM.Extension import Extension
 from UM.Preferences import Preferences
 from UM.Logger import Logger
@@ -32,6 +35,17 @@ class FirmwareUpdateChecker(Extension):
         if Preferences.getInstance().getValue("info/automatic_update_check"):
             ContainerRegistry.getInstance().containerAdded.connect(self._onContainerAdded)
 
+        self._download_url = None
+
+    ##  Callback for the message that is spawned when there is a new version.
+    def _onActionTriggered(self, message, action):
+        if action == "download":
+            if self._download_url is not None:
+                QDesktopServices.openUrl(QUrl(self._download_url))
+
+    def _onSetDownloadUrl(self, download_url):
+        self._download_url = download_url
+
     def _onContainerAdded(self, container):
         # Only take care when a new GlobalStack was added
         if isinstance(container, GlobalStack):
@@ -45,5 +59,7 @@ class FirmwareUpdateChecker(Extension):
     #   \param silent type(boolean) Suppresses messages other than "new version found" messages.
     #                               This is used when checking for a new firmware version at startup.
     def checkFirmwareVersion(self, container = None, silent = False):
-        job = FirmwareUpdateCheckerJob(container = container, silent = silent, url = self.JEDI_VERSION_URL)
+        job = FirmwareUpdateCheckerJob(container = container, silent = silent, url = self.JEDI_VERSION_URL,
+                                       callback = self._onActionTriggered,
+                                       set_download_url_callback = self._onSetDownloadUrl)
         job.start()