Catch PermissionError when writing workspaces

We'll want to give a proper error message then. We have no mechanism right now to show a message on the screen particular to this error. Instead we'll let it fail (the user sees a message that writing fails) and put a message in the log why it failed.

Fixes Sentry error CURA-DK.

plugins/3MFWriter/ThreeMFWorkspaceWriter.py

@@ -1,4 +1,4 @@
-# Copyright (c) 2018 Ultimaker B.V.
+# Copyright (c) 2020 Ultimaker B.V.
 # Cura is released under the terms of the LGPLv3 or higher.
 
 import configparser
@@ -6,6 +6,7 @@ from io import StringIO
 import zipfile
 
 from UM.Application import Application
+from UM.Logger import Logger
 from UM.Preferences import Preferences
 from UM.Settings.ContainerRegistry import ContainerRegistry
 from UM.Workspace.WorkspaceWriter import WorkspaceWriter
@@ -25,6 +26,7 @@ class ThreeMFWorkspaceWriter(WorkspaceWriter):
         mesh_writer = application.getMeshFileHandler().getWriter("3MFWriter")
 
         if not mesh_writer:  # We need to have the 3mf mesh writer, otherwise we can't save the entire workspace
+            Logger.error("3MF Writer class is unavailable. Can't write workspace.")
             return False
 
         # Indicate that the 3mf mesh writer should not close the archive just yet (we still need to add stuff to it).
@@ -59,6 +61,7 @@ class ThreeMFWorkspaceWriter(WorkspaceWriter):
         preferences_string = StringIO()
         temp_preferences.writeToFile(preferences_string)
         preferences_file = zipfile.ZipInfo("Cura/preferences.cfg")
+        try:
             archive.writestr(preferences_file, preferences_string.getvalue())
 
             # Save Cura version
@@ -77,6 +80,9 @@ class ThreeMFWorkspaceWriter(WorkspaceWriter):
 
             # Close the archive & reset states.
             archive.close()
+        except PermissionError:
+            Logger.error("No permission to write workspace to this stream.")
+            return False
         mesh_writer.setStoreArchive(False)
         return True