Merge remote-tracking branch 'origin/flask_rest' into flask_rest

freqtrade/configuration.py

@@ -61,11 +61,9 @@ class Configuration(object):
             with open(path) as file:
                 conf = json.load(file)
         except FileNotFoundError:
-            logger.critical(
-                'Config file "%s" not found. Please create your config file',
-                path
-            )
-            exit(0)
+            raise OperationalException(
+                'Config file "{}" not found!'
+                ' Please create a config file or check whether it exists.'.format(path))
 
         if 'internals' not in conf:
             conf['internals'] = {}
@@ -240,9 +238,8 @@ class Configuration(object):
         exchange = config.get('exchange', {}).get('name').lower()
         if exchange not in ccxt.exchanges:
 
-            exception_msg = 'Exchange "{}" not supported.\n' \
-                            'The following exchanges are supported: {}'\
-                .format(exchange, ', '.join(ccxt.exchanges))
+            exception_msg = f'Exchange "{exchange}" not supported.\n' \
+                            f'The following exchanges are supported: {", ".join(ccxt.exchanges)}'
 
             logger.critical(exception_msg)
             raise OperationalException(