update problem

I updated today one of my leap15.1 computers and I received this message:
patch:openSUSE-2020-157-1.noarch conflicts with python-nbxmpp.noarch
Is this a bug or is this python-nbxmpp.noarch package not yet up to date?

I used YAST to uninstall python-nbxmpp expecting an error message to tell me where this package is used. Nothing came so I went ahead and removed this package and afterwards the update went through without problem. I don’t know where this package came from. THis is quite an old machine and to install other packages I had to use different repos. Some of these software packages are no longer on this machine. I expect instead of upgrading when a new version comes out I should make a clean install to avoid these problems in future.