src/should.py: fix Python 3.4 compatibility on 'j0:' tests

fix #63
as in https://github.com/GNS3/gns3-server/issues/847
3 jobs for 63-fix-python34 in 33 seconds (queued for 6 seconds)
Status Job ID Name Coverage
  Unit
passed #10314
unit

00:00:08

 
  Demo
passed #10315
demo

00:00:11

 
  Coverage
passed #10316
coverage

00:00:13

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