The make command will now find make.py in the pylib directory, so
developing make and make.py should be a bit less tricky now. (And make
will now install make.py properly, even if it's never been installed
before.)
I've stopped trying to use the built-in format() function, and I've
replaced it with something that works consistently across all Python
versions (and works the way I want it to).

Use {number} to get the args[number]. Use {name} to get kwargs[name].
Use {} to get the next field (starting with 1, not 0), so you can use
this for relative field references ...

... which gives me the idea to allow {-number} and {+number} fieldspecs
to *really* support relative field references. Maybe next time.