[tex-live] lyluatex package

[Karl Berry]

    kpse.set_program_name("kpsewhich --format=lua")

It turns out that 
  kpse.set_program_name("foobar")
also fails the assertion. Any program name that doesn't exist.

I made it so kpathsea simply quits (gracefully) if passed a nonexistent
program name at this level. Since before it failed an assertion, I
suppose that won't cause problems.

It doesn't affect kpsewhich's --progname option, which can still be
passed anything, as far as I can see. LuaTeX does a more complete
reinitialization of the whole system. 

Thanks again for the report. --karl