Logging errors in promises

promise.js

let console = (Cu.import("resource://gre/modules/devtools/Console.jsm", {})).console;

// ...

/**
 * Internal utility: Decorates given `f` function, so that on exception promise
 * rejected with thrown error is returned.
 */
function attempt(f) {
  return function effort(input) {
    try {
      return f(input);
    }
    catch(error) {
console.error(error);
      return rejected(error);
    }
  };
}