Fixed refresh problem following 9c5f835b031e, 9622418ac28c, c67488bd8134 : force redraw only through EVT_PAINT event and use wxPaintDC, as described in wx documentation

<?xml version='1.0' encoding='utf-8'?>
<BaseParams xmlns:xsd="http://www.w3.org/2001/XMLSchema" IEC_Channel="0" Name="py_ext_0"/>