Migrated demo code to not import string module. (Patch from Kevin Altis)

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/branches/WX_2_4_BRANCH@18718 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

wxPython/demo/XMLtreeview.py

@@ -1,5 +1,5 @@
 
-import string, sys
+import sys
 
 py2 = sys.version[0] == '2'
 
@@ -76,7 +76,7 @@ else:
             self.nodeStack = self.nodeStack[:-1]
 
         def CharacterData(self, data ):
-            if string.strip(data):
+            if data.strip():
                 if py2:
                     data = data.encode()
                 self.AppendItem(self.nodeStack[-1], data)