[Koha] Upgrade from 3.10 to 3.14x

Hi , I have 2 servers: server *A* and server *B *. server A has koha 3.10 installation ( packages ) server B has koha 3.14 installation (packages ) . I take the backup files from (/var/spool/koha/library ) from server A . and restore them on server B . after that I get an error message : ERROR 1396 (HY000) at line 1: Operation DROP USER failed for 'koha_library'@ '%' I make the upgrade schema after that. koha-upgrade-schema library . no errors . and Koha is working, it seems that there is no problem . but I don't know what is that error message means ? please let me know if I miss something . or that is normal . Many Thanks :) . -- *Karam Qubsi*