removeHandler(cb) {
    let index = handlers.indexOf(cb);
    if (index < 0) {
      return;
    }

    handlers.splice(index, 1);
    captureExit.offExit(cb);

    if (handlers.length === 0) {
      teardownSignalsTrap();
    }
  }
Remove process interruption handler

If there are no remaining handlers after removal
then clean up all the process interruption signal listeners

@private
@method removeHandler
@param {function} cb   Callback to be removed