Adjust tests to 3tuple return value from async method

freqtrade/exchange/__init__.py

@@ -518,6 +518,7 @@ class Exchange(object):
         input_coroutines = [self._async_get_candle_history(
             pair, tick_interval, since) for since in
             range(since_ms, arrow.utcnow().timestamp * 1000, one_call)]
+
         tickers = await asyncio.gather(*input_coroutines, return_exceptions=True)
 
         # Combine tickers