_readyToRunTask(...args) {
    if (
      Object.keys(this.tasks).some(key => {
        const task = this.tasks[key]
        return task.running === true && task.blocking === true
      })
    )
      return false

    return super._readyToRunTask(...args) // eslint-disable-line no-underscore-dangle
  }
Test if we are ready to run a task.
Implement blocking task.