I had this issue, but it did not concern the debian-sys-maint credentials. In my case I had defined a non-standard socket location in my /etc/mysql/my.cnf, and the socket location in /etc/mysql/debian.cnf was different. Therefore the server could not be stopped nor started during upgrade.
I don't know the significance of "debian.cnf" -- I didn't create it. Where did it come from, and for what is it used? It seems like a fairly fundamental problem that conflicts between these two files could make my entire system un-upgradeable.
I had this issue, but it did not concern the debian-sys-maint credentials. In my case I had defined a non-standard socket location in my /etc/mysql/my.cnf, and the socket location in /etc/mysql/ debian. cnf was different. Therefore the server could not be stopped nor started during upgrade.
I don't know the significance of "debian.cnf" -- I didn't create it. Where did it come from, and for what is it used? It seems like a fairly fundamental problem that conflicts between these two files could make my entire system un-upgradeable.