Catch 'clipboard already open' errors in editors

Apparently following commits have not fixed the problem completely,
because it still happens (although not so often).

changeset: 2019:b8f795bdfe9f
user: Andrey Skvortsov <andrej.skvortzov@gmail.com>
date: Fri May 25 17:40:29 2018 +0300
summary: fix hangs on mouse selection in case if wxPython uses wxWidgets with GTK3+ support

changeset: 2018:5ce6d08ff2c7
user: Andrey Skvortsov <andrej.skvortzov@gmail.com>
date: Fri May 25 17:23:15 2018 +0300
summary: make clipboard open minimal time as wxPython documentation recommends

--- a/IDEFrame.py	Wed Jun 27 10:58:45 2018 +0300
+++ b/IDEFrame.py	Wed Jun 27 13:57:03 2018 +0300
@@ -944,7 +944,11 @@
         if not wx.TheClipboard.IsOpened():
             dataobj = wx.TextDataObject()
             if wx.TheClipboard.Open():
-                success = wx.TheClipboard.GetData(dataobj)
+                success = False
+                try:
+                    success = wx.TheClipboard.GetData(dataobj)
+                except wx._core.PyAssertionError:
+                    pass
                 wx.TheClipboard.Close()
                 if success:
                     data = dataobj.GetText()