This is a rework of the SSLErrorDialog in the process of removing ConfirmationDialogDoubleCheck from Gajim.
SSLErrorDialog
ConfirmationDialogDoubleCheck
I added a test for this dialog, which can be run by python3 -m test.gtk.ssl_error_dialog.
python3 -m test.gtk.ssl_error_dialog
Note: I have not tested this dialog other than using the test provided.