lib/utils.js
function safeExec(cmd, cb) {
    try {
      utils._exec(cmd, cb);
    } catch (e) {
      cb(e, null);
    }
  }
function safeExec(cmd, cb) {
    try {
      utils._exec(cmd, cb);
    } catch (e) {
      cb(e, null);
    }
  }
Node's built in `exec` function sometimes throws outright,
and sometimes has a callback with an error,
depending on the type of error.

This unifies that interface.