Comment 15 for bug 1871960

I tested an upgrade from Bionic to Focal with -proposed enabled (I had to remove the disabling of -proposed in DistUpgradeController.py) and did not encounter any of the following error messages:

GLib-GObject-WARNING **: specified class size for type 'PangoCairoFcFont' is smaller than the parent type's 'PangoFcFont' class size at /usr/lib/x86_64-linux-gnu/perl5/5.30/Glib/Object/Introspection.pm line 67.
GLib-GObject-CRITICAL **: g_type_add_interface_static: assertion 'G_TYPE_IS_INSTANTIATABLE (instance_type)' failed at /usr/lib/x86_64-linux-gnu/perl5/5.30/Glib/Object/Introspection.pm line 67.
GLib-CRITICAL **: g_once_init_leave: assertion 'result != 0' failed at /usr/lib/x86_64-linux-gnu/perl5/5.30/Glib/Object/Introspection.pm line 67.
GLib-GObject-CRITICAL **: g_object_new_valist: assertion 'G_TYPE_IS_OBJECT (object_type)' failed at /usr/lib/x86_64-linux-gnu/perl5/5.30/Glib/Object/Introspection.pm line 67.

I had seen them when I tried upgrading the same virtual machine when -proposed was not enabled. Attached you'll find my apt-term.log from the successful upgrade.