odd cut and paste error fixed.

freqtrade/exchange/__init__.py

@@ -95,6 +95,11 @@ class Exchange(object):
         except (KeyError, AttributeError):
             raise OperationalException(f'Exchange {name} is not supported')
 
+        # check if config requests sanbox, if so use ['test'] from url
+        if (exchange_config.get('sandbox')):
+            api.urls['api'] = api.urls['test'];
+            # exchange.urls['api'] = exchange.urls['test'];
+
         return api
 
     @property