Am new to fedora and this error really wasted a lot of my time, so i thought i should document it.

sudoers file is located in the etc folder.

open terminal and go to etc location


gedit sudoers

on line 77 u will find this

root    ALL=(ALL)     ALL

on line 78 add ur user like this

nauman ALL=(ALL)  ALL

save the file and exit.

nauman is ur user that u want to include in the sudoers file and because of which u r getting the not in sudoers file error.

this way u can solve the stupid error in fedora and continue with ur actual work.

hope this helps.