llvm80-8.0.1_3 needs Python 3.6 at least, but 2.7 was specified.

[Chris]

I'm testing modifications of ports I maintain in
a jail. I have nothing in make.conf(5) except
DEVELOPER=true
But I get messages regarding python versions like:
llvm80-8.0.1_3 needs Python 3.6 at least, but 2.7 was specified.
But I make no demands on versions.
What causes this, and how can I stop it. :)

Thanks!

--Chris