API Error handling

Token data is stale according to Kay. While investigating this, I saw the following in the logs. Perhaps this is preventing updates of token data.

Traceback (most recent call last):
  File "logic/scripts/update_token_insight.py", line 442, in <module>
    token_stats.compute_ogn_stats()
  File "/app/logic/scripts/token_stats.py", line 280, in compute_ogn_stats
    ogn_staked_data = fetch_onchain_staking_stats_by_duration()
  File "/app/logic/scripts/token_stats.py", line 92, in fetch_onchain_staking_stats_by_duration
    response = raw_json.json()
  File "/app/.heroku/python/lib/python2.7/site-packages/requests/models.py", line 897, in json
    return complexjson.loads(self.text, **kwargs)
  File "/app/.heroku/python/lib/python2.7/json/__init__.py", line 339, in loads
    return _default_decoder.decode(s)
  File "/app/.heroku/python/lib/python2.7/json/decoder.py", line 364, in decode
    obj, end = self.raw_decode(s, idx=_w(s, 0).end())
  File "/app/.heroku/python/lib/python2.7/json/decoder.py", line 382, in raw_decode
    raise ValueError("No JSON object could be decoded")
ValueError: No JSON object could be decoded

The README has an example for ./logic/scripts/token_stats.py, but that script is not being run with task scheduler on heroku. Not clear yet if that's related.

Start with the traceback in logic/scripts/token_stats.py, especially fetch_onchain_staking_stats_by_duration(), and trace its call from logic/scripts/update_token_insight.py. Compare the README example for token_stats.py with the Heroku task scheduler configuration. Done means identifying whether the JSON error or missing scheduled task prevents token updates and documenting or fixing the confirmed cause.