How do I correct this problem that happens when I submit an algorithm using sentdex to the Contest? If necessary, I can provide more details on the algorithm, but it's based on the Algorithmic Trading tutorial.
Backtest Exception NoDataAvailable: Backtest began on 2016-08-31 and
ended on 2018-08-31, but some of the requested datasets do not have
data for this time. The datasets are: sentdex.sentiment_free:
start=2013-06-01, end=2018-08-02. Your backtest must begin on or
after: 2013-06-01 and end on or before: 2018-08-02.