It’s just that every sudoers file I’ve ever read has the following line:
# This file MUST be edited with the ‘visudo’ command as root.

But it turns out that I’m wrong. `visudo` has the ability invoke whatever editor you have stored in your $EDITOR variable.

from the man page,

env_editor
If set, visudo will use the value of the EDITOR or VISUAL environment vari-
ables before falling back on the default editor list. Note that this may
create a security hole as it allows the user to run any arbitrary command as
root without logging. A safer alternative is to place a colon-separated list
of editors in the editor variable. visudo will then only use the EDITOR or
VISUAL if they match a value specified in editor. This flag is on by
default.

So you can use any editor you like. But you still *have* to use the `visudo` command.

So …

export EDITOR=nano
sudo visudo

nano works fine. However, I have it on good authority that every time someone uses emacs, a puppy somewhere gets shot. Harsh. But true.

you have to learn some basic vi keystrokes but that’s better than fubar’ing sudoers!