Things always get weird as one's installed distribution gets crusty.
My Fedora Core 27 installation recently started whining about conflicts
between nmh and vi. Surprised me.
I don't know if anybody has given any thought as to what should be a
dependency and what shouldn't. Seems to me that dependencies should
be things necessary to build, install, and run (libraries) a program.
Not other companion programs on the system. I think that a run-time
error message of the form "No editor defined. Set EDITOR or VISUAL
in your environment , or Editor in your .mh_profile" is a better way
Of course, I could be completely off base here if vi is actually used
as part of the build process. But that would seem weird to me too.