Plone 5.2 execfile error bin/test

I'm porting some packages to Plone 5.2, and the recipe test is generating the old execfile method..

so I need to change from:

execfile(os.environ['PYTHONSTARTUP'])

to:

filename = os.environ['PYTHONSTARTUP']
exec(compile(open(filename, "rb").read(), filename, 'exec'))

The weird thing is that my version of zc.recipe.testunner (2.1) and zc.buildout (2.13.2) should generate it right as far as I found..

Any idea of what am I missing?

Plone Foundation Code of Conduct