example

gistfile1.js

function thingy(cb)
  doAsyncThing("arg1", "arg2", "argn", andWarnOnError(log, cb))
}

function andWarnOnError (log, cb) {
  return function (er, result) {
    if (er) {
      log.warn("install", "Couldn't install optional dependency:", er.message)
      log.verbose("install", er.stack)
    }
    cb(null, result)
  }
}