wxGUI: import missing module

git-svn-id: https://svn.osgeo.org/grass/grass/trunk@50714 15284696-431f-4ddb-bdfa-cd5b030d7da7

gui/wxpython/gui_core/mapdisp.py

@@ -20,6 +20,7 @@ This program is free software under the GNU General Public License
 """
 
 import os
+import sys
 
 import wx
 import wx.aui