This is no longer needed now, maybe since Zope4. Which is a good thing
because this option cannot be used on python3

See merge request nexedi/erp5!1912

so that Tester methods will have some __roles__ as Getter.

because str(float) result is different between py2/py3.

* py2
>>> str(-0.8999999999999999)
'-0.9'

* py3
>>> str(-0.8999999999999999)
'-0.8999999999999999'