fix undefined name xtpGateway

examples/VnTrader/run.py

@@ -1,6 +1,10 @@
 # encoding: UTF-8
 
 # 重载sys模块，设置默认字符串编码方式为utf8
+try:
+    reload         # Python 2
+except NameError:  # Python 3
+    from importlib import reload
 import sys
 reload(sys)
 sys.setdefaultencoding('utf8')
@@ -19,7 +23,9 @@ from vnpy.trader.uiMainWindow import MainWindow
 from vnpy.trader.gateway import (ctpGateway, oandaGateway,
                                  ibGateway)
 
-if system == 'Windows':
+if system == 'Linux':
+    from vnpy.trader.gateway import xtpGateway
+elif system == 'Windows':
     from vnpy.trader.gateway import (femasGateway, xspeedGateway,
                                      futuGateway, secGateway)