'Python executable default/custom radio button has been toggled'

def python_executable_switched(self, custom):

    def_pyexec = get_python_executable()
    cust_pyexec = self.pyexec_edit.text()
    if (not is_text_string(cust_pyexec)):
        cust_pyexec = to_text_string(cust_pyexec.toUtf8(), 'utf-8')
    if (def_pyexec != cust_pyexec):
        if custom:
            self.warn_python_compatibility(cust_pyexec)
