Skip tests for Python3.
@jerome @vpelletier , Tests do pass at https://nexedi.erp5.net/test_result_module/20200122-713A91C9/view?ignore_layout:int=1 /reviewed-on nexedi/caucase!12
@jerome @vpelletier , Tests do pass at https://nexedi.erp5.net/test_result_module/20200122-713A91C9/view?ignore_layout:int=1 /reviewed-on nexedi/caucase!12