test-iot.bbclass: Python3 compatibility
test-iot.bbclass: Python3 compatibility

"except Foo, ex" is no longer supported in Python3. "except Foo as ex" works
in both Python2 and Python3.

Signed-off-by: Patrick Ohly <0fc9d825c622b2a5ac5160289c29f03654b10648@intel.com>

wanghongjuan/meta-iotqa-1,ostroproject/meta-iotqa,ostroproject/meta-iotqa,ostroproject/meta-iotqa,wanghongjuan/meta-iotqa-1,ostroproject/meta-iotqa,wanghongjuan/meta-iotqa-1,wanghongjuan/meta-iotqa-1,ostroproject/meta-iotqa,wanghongjuan/meta-iotqa-1