[Koha] Upgrade from 3.10 to 3.14x

[Karam Qubsi]

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*