'execfile' is python-2-only. 'exec/open' works for both python2 and python3.
--- a/gui-wx/wxpython.cpp
+++ b/gui-wx/wxpython.cpp
@@ -3356,7 +3388,7 @@ void RunPythonScript(const wxString& filepath)
     // for the global namespace so that this script cannot change the
     // globals of a caller script (which is possible now that RunScript
     // is re-entrant)
-    wxString command = wxT("execfile('") + fpath + wxT("',{})");
+    wxString command = wxT("exec(open('") + fpath + wxT("').read(),{})");
     PyRun_SimpleString(command.mb_str(wxConvLocal));
     // don't use wxConvUTF8 in above line because caller has already converted
     // filepath to decomposed UTF8 if on a Mac