use only pytest < 3

[atarkowska]

What this PR does

try to fix pytest version

Testing this PR

go to:

• https://ci.openmicroscopy.org/job/OMERO-DEV-breaking-integration-Python27
• https://ci.openmicroscopy.org/job/OMERO-DEV-merge-integration-Python27

and check which version is used when tests are run, it is listed in:

05:24:34 ============================= test session starts ==============================
05:24:34 platform linux2 -- Python 2.7.5, pytest-3.0.3, py-1.4.31, pluggy-0.4.0 ...

Related reading

#4826

LIMITATIONS:

for some reason merge build has pytest-2.8.1 installed, that is not very clear to me where is that exactly. This PR run on merge didn't change anything, see #4886 (comment)

[joshmoore]

Is pytest causing any other issues? If none, cfbfac9 is probably we should be doing anyway in our tests. i.e. this could be our fault not pytests.

[atarkowska]

do you want me to drop pytest cap and cherry-pick POLICY_FIXTURES to try out?

[atarkowska]

I also don't understand why merge integration shows:

03:44:45 ============================= test session starts ==============================
03:44:45 platform linux2 -- Python 2.7.5, pytest-2.8.1, py-1.4.30, pluggy-0.3.1 -- /opt/hudson

virtualenv has no pytests installed

[jburel]

This was the comment on the initial PR
#4826 (comment)
Why is it an issue now?

[joshmoore]

I don't think pytest-dev/pytest#1908 was enough. It only made it possible to accept str or unicode, but here we're passing in non-string arguments. They need to be wrapped as in cfbfac9

[jburel]

@joshmoore thanks

[atarkowska]

#4853 cherry-picked

[atarkowska]

--rebased-to #4894

[joshmoore]

Filed a card to remember to uncap pytest: https://trello.com/c/TcfoKhbw/723-uncap-pytest . Merging.