Tarball export should show the errors through an error dialog
Submitted by Jeff F.T.
Assigned to Jeff F.T.
In project.py's exportProject method, there is a giant try-catch that doesn't communicate the actual error. We should modify this (see also mainwindow.py's _exportProjectAsTarCb) so that errors are caught and show in an error dialog.
Imported from https://bugzilla.gnome.org/show_bug.cgi?id=707202