Refactor refresh_pairs to exchange and fix tests

freqtrade/exchange/__init__.py

@@ -389,6 +389,16 @@ class Exchange(object):
         logger.info("downloaded %s with length %s.", pair, len(data))
         return data
 
+    def refresh_tickers(self, pair_list: List[str], ticker_interval: str) -> bool:
+        """
+        Refresh tickers asyncronously and return the result.
+        """
+        logger.debug("Refreshing klines for %d pairs", len(pair_list))
+        asyncio.get_event_loop().run_until_complete(
+            self.async_get_candles_history(pair_list, ticker_interval))
+
+        return True
+
     async def async_get_candles_history(self, pairs: List[str],
                                         tick_interval: str) -> List[Tuple[str, List]]:
         """Download ohlcv history for pair-list asyncronously """