title: RuntimeError: There is no current event loop in thread in async + apscheduler
body: <p>I have a async function and need to run in with apscheduller every N minutes.
  There is a python code below</p>
  
  <pre><code>URL_LIST = ['&lt;url1&gt;',
              '&lt;url2&gt;',
              '&lt;url2&gt;',
              ]
  
  def demo_async(urls):
      """Fetch list of web pages asynchronously."""
      loop = asyncio.get_event_loop() # event loop
      future = asyncio.ensure_future(fetch_all(urls)) # tasks to do
      loop.run_until_complete(future) # loop until done
  
  async def fetch_all(urls):
      tasks = [] # dictionary of start times for each url
      async with ClientSession() as session:
          for url in urls:
              task = asyncio.ensure_future(fetch(url, session))
              tasks.append(task) # create list of tasks
          _ = await asyncio.gather(*tasks) # gather task responses
  
  async def fetch(url, session):
      """Fetch a url, using specified ClientSession."""
      async with session.get(url) as response:
          resp = await response.read()
          print(resp)
  
  if __name__ == '__main__':
      scheduler = AsyncIOScheduler()
      scheduler.add_job(demo_async, args=[URL_LIST], trigger='interval', seconds=15)
      scheduler.start()
      print('Press Ctrl+{0} to exit'.format('Break' if os.name == 'nt' else 'C'))
  
      # Execution will block here until Ctrl+C (Ctrl+Break on Windows) is pressed.
      try:
          asyncio.get_event_loop().run_forever()
      except (KeyboardInterrupt, SystemExit):
          pass
  </code></pre>
  
  <p>But when i tried to run it i have the next error info</p>
  
  <pre><code>Job "demo_async (trigger: interval[0:00:15], next run at: 2017-10-12 18:21:12 +04)" raised an exception.....
  ..........\lib\asyncio\events.py", line 584, in get_event_loop
      % threading.current_thread().name)
  RuntimeError: There is no current event loop in thread '&lt;concurrent.futures.thread.ThreadPoolExecutor object at 0x0356B150&gt;_0'.
  </code></pre>
  
  <p>Could you please help me with this? 
  Python 3.6, APScheduler 3.3.1, </p>