reduce complexity of start_download_data() for flake8

freqtrade/commands/data_commands.py

@@ -11,7 +11,7 @@ from freqtrade.data.history import (convert_trades_to_ohlcv, refresh_backtest_oh
                                     refresh_backtest_trades_data)
 from freqtrade.enums import CandleType, RunMode, TradingMode
 from freqtrade.exceptions import OperationalException
-from freqtrade.exchange import market_is_active, timeframe_to_minutes
+from freqtrade.exchange import Exchange, market_is_active, timeframe_to_minutes
 from freqtrade.freqai.utils import setup_freqai_spice_rack
 from freqtrade.plugins.pairlist.pairlist_helpers import dynamic_expand_pairlist, expand_pairlist
 from freqtrade.resolvers import ExchangeResolver
@@ -68,7 +68,19 @@ def start_download_data(args: Dict[str, Any]) -> None:
         exchange.validate_timeframes(timeframe)
 
     try:
+        pairs_not_available = download_trades(exchange, expanded_pairs, config, timerange)
 
+    except KeyboardInterrupt:
+        sys.exit("SIGINT received, aborting ...")
+
+    finally:
+        if pairs_not_available:
+            logger.info(f"Pairs [{','.join(pairs_not_available)}] not available "
+                        f"on exchange {exchange.name}.")
+
+
+def download_trades(exchange: Exchange, expanded_pairs: list,
+                    config: Dict[str, Any], timerange: TimeRange) -> list:
     if config.get('download_trades'):
         if config.get('trading_mode') == 'futures':
             raise OperationalException("Trade download not supported for futures.")
@@ -100,13 +112,7 @@ def start_download_data(args: Dict[str, Any]) -> None:
             prepend=config.get('prepend_data', False)
         )
 
-    except KeyboardInterrupt:
-        sys.exit("SIGINT received, aborting ...")
-
-    finally:
-        if pairs_not_available:
-            logger.info(f"Pairs [{','.join(pairs_not_available)}] not available "
-                        f"on exchange {exchange.name}.")
+    return pairs_not_available
 
 
 def start_convert_trades(args: Dict[str, Any]) -> None: