Fuel web incompatibility with pytest 2.8

[Vladimir Sharshov]

Problem in nailgun/extensions/cluster_upgrade/tests/test_validators.py. For some reason string

```from nailgun.errors import errors``` raise such error with new pytest.

Source: https://github.com/stackforge/fuel-web/blob/master/nailgun/nailgun/extensions/cluster_upgrade/tests/test_validators.py#L22

More details:

ERROR collecting nailgun/extensions/cluster_upgrade/tests/test_validators.py
nailgun/.tox/py26/lib/python2.6/site-packages/_pytest/runner.py:149: in __init__
    self.result = func()
nailgun/.tox/py26/lib/python2.6/site-packages/_pytest/main.py:437: in _memocollect
    return self._memoizedcall('_collected', lambda: list(self.collect()))
nailgun/.tox/py26/lib/python2.6/site-packages/_pytest/main.py:317: in _memoizedcall
    res = function()
nailgun/.tox/py26/lib/python2.6/site-packages/_pytest/main.py:437: in <lambda>
    return self._memoizedcall('_collected', lambda: list(self.collect()))
nailgun/.tox/py26/lib/python2.6/site-packages/_pytest/python.py:575: in collect
    return super(Module, self).collect()
nailgun/.tox/py26/lib/python2.6/site-packages/_pytest/python.py:435: in collect
    l.sort(key=lambda item: item.reportinfo()[:2])
nailgun/.tox/py26/lib/python2.6/site-packages/_pytest/python.py:435: in <lambda>
    l.sort(key=lambda item: item.reportinfo()[:2])
nailgun/.tox/py26/lib/python2.6/site-packages/_pytest/python.py:371: in reportinfo
    assert isinstance(lineno, int)
E assert isinstance(<class 'nailgun.errors.compat_co_firstlineno'>, int)

Affect CI jobs: https://ci.fuel-infra.org/job/verify-fuel-web/

[Vladimir Sharshov (vsharshov)]

Related review: https://review.openstack.org/#/c/225461/

[Vladimir Sharshov (vsharshov)]

It can also affect 7.0 as well.

[OpenStack Infra (hudson-openstack)]

Related fix proposed to branch: stable/7.0
Review: https://review.openstack.org/225497

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/225564

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/225564
Committed: https://git.openstack.org/cgit/stackforge/fuel-web/commit/?id=9757292c3b7f2a8d955fbe2cc1673a2baac702e5
Submitter: Jenkins
Branch: master

commit 9757292c3b7f2a8d955fbe2cc1673a2baac702e5
Author: Sebastian Kalinowski <email address hidden>
Date: Mon Sep 21 09:35:40 2015 +0200

    ErrorsFactory returns only defined errors

    ErrorsFactory had __getattr__ method that was used to always
    return any error (if it doesn't existed, it created a new one).
    This was causing "hasattr" to return 'True' for every check.
    Due to this any code, that wanted to check for some unique attributes
    in ErrorsFactory was working incorrectly. This was the case for
    a py.test library when scannig code when looking for tests.
    Now this behavior has been removed. This uncovered new bugs
    which was fixed.

    Change-Id: I3c9be96dbcc535ea9c730d29b065479cc318fd9f
    Closes-Bug: #1497664

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: stable/7.0
Review: https://review.openstack.org/225683

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/225683
Committed: https://git.openstack.org/cgit/stackforge/fuel-web/commit/?id=52ed7e621cffe8b448b28d3d98a5ec722b75a3e1
Submitter: Jenkins
Branch: stable/7.0

commit 52ed7e621cffe8b448b28d3d98a5ec722b75a3e1
Author: Sebastian Kalinowski <email address hidden>
Date: Mon Sep 21 09:35:40 2015 +0200

    ErrorsFactory returns only defined errors

    ErrorsFactory had __getattr__ method that was used to always
    return any error (if it doesn't existed, it created a new one).
    This was causing "hasattr" to return 'True' for every check.
    Due to this any code, that wanted to check for some unique attributes
    in ErrorsFactory was working incorrectly. This was the case for
    a py.test library when scannig code when looking for tests.
    Now this behavior has been removed. This uncovered new bugs
    which was fixed.

    Change-Id: I3c9be96dbcc535ea9c730d29b065479cc318fd9f
    Closes-Bug: #1497664
    (cherry picked from commit 9757292c3b7f2a8d955fbe2cc1673a2baac702e5)

[OpenStack Infra (hudson-openstack)]

Change abandoned by Vladimir Sharshov (<email address hidden>) on branch: stable/7.0
Review: https://review.openstack.org/225497
Reason: Final solution: https://review.openstack.org/#/c/225461/,

[OpenStack Infra (hudson-openstack)]

Change abandoned by Vladimir Sharshov (<email address hidden>) on branch: master
Review: https://review.openstack.org/225461
Reason: Final solution: https://review.openstack.org/#/c/225461

[Tatyanka (tatyana-leontovich)]

https://ci.fuel-infra.org/job/verify-fuel-web/5036/ - according to the last runs, move to fix released