ImportError: No module named 'simplejson'

Configuration
1

I am trying to use Alpha Vantage sensor. This is my configuration:

  - platform: alpha_vantage
    api_key: !secret av_api_key
    symbols:
      - name: American International Group Inc
        currency: USD
        symbol: AIG

I receive the following error when I restart my HA:

Error while setting up platform alpha_vantage

Traceback (most recent call last):
  File "/srv/homeassistant/lib/python3.5/site-packages/homeassistant/helpers/entity_platform.py", line 82, in async_setup
    SLOW_SETUP_MAX_WAIT, loop=hass.loop)
  File "/usr/lib/python3.5/asyncio/tasks.py", line 400, in wait_for
    return fut.result()
  File "/usr/lib/python3.5/asyncio/futures.py", line 293, in result
    raise self._exception
  File "/usr/lib/python3.5/concurrent/futures/thread.py", line 55, in run
    result = self.fn(*self.args, **self.kwargs)
  File "/srv/homeassistant/lib/python3.5/site-packages/homeassistant/components/sensor/alpha_vantage.py", line 69, in setup_platform
    from alpha_vantage.timeseries import TimeSeries
  File "/srv/homeassistant/lib/python3.5/site-packages/alpha_vantage/timeseries.py", line 1, in <module>
    from .alphavantage import AlphaVantage as av
  File "/srv/homeassistant/lib/python3.5/site-packages/alpha_vantage/alphavantage.py", line 17, in <module>
    from simplejson import loads
ImportError: No module named 'simplejson'

I checked lots of articles. I think I installed smplejson, but it does not work.
Can you help?