root' is not allowed to commit files

Until recently, I've been able to log in as a normal user, use "su -l" 
to become root, edit a file, then check it in using CVS. Now, I get 
this message:

cvs [commit aborted]: 'root' is not allowed to commit files

The exact command that fails is:
-su(root)# cvs ci -F ~/tmp/ci.txt /etc/network/interfaces

I've tried adding a writers file in $CVSROOT/CVSROOT/writers with these 
lines:
bryan
root

but the problem persists. Its acting like CVS can't find the original 
user name.

As recently as last January - 1/10/17 - the checkin procedure worked 
just fine.

Any help will be greatly appreciated.

Thanks,
-- 
Bryan
-
Trump Revolution: Spelled with the middle finger capitalized.