Forward port recent changes on the 2.8 branch to HEAD

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@46083 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

wxPython/tests/TreeMixinTest.py

@@ -1,4 +1,9 @@
-import wx, wx.gizmos, wx.lib.customtreectrl, unittest, treemixin
+import wx, wx.gizmos, wx.lib.customtreectrl, unittest
+try:
+    import treemixin 
+except ImportError:
+    from wx.lib.mixins import treemixin
+
 
 
 # VirtualTree tests