fix splash loading with wx3.0

Previously only gray square was shown. Apparently to show splash screen several calls of wx.Yield() are necessary.
Unfortunately splash.IsShowOnScreen() returns always 1 regardless of whether splash is on the screen or not.
this fix is a dirty hack. It just process all events after splash is created during 0.3 seconds.

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from py_ext import *

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from PythonEditor import PythonEditor

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from PythonFileCTNMixin import PythonFileCTNMixin