Bareword warn in compat.lua is a "strict" violation

[tkoeppe]

The bareword warn in

Penlight/lua/pl/compat.lua

Line 228 in a7b9f88

if not warn then -- luacheck: ignore

is an undefined variable, which some "strictness" checking tools (such as https://github.com/deepmind/strict/) diagnose and reject.

I believe you can achieve the same effect without use of potentially undefined variables by replacing

if not warn then

with:

if not rawget(_G, 'warn') then

Would you perhaps be able to make that change?

Thank you!