joyent/node — pull request #7254 by indutny (2014-03-06 12:03:21+00:00)
Title: util: format as Error if instanceof Error

Conflicts:
lib/util.js
test/simple/test-util-format.js

This is a backport to fix #7253

@tjfontaine : it seems to be pretty harmless, but I'm afraid to decide if it is a bug fix or a feature.