py34 calling __eq__ for !=

[Thang Pham]

There seems to be a problem in python 3.4 with the mix-in class ComparableVersionedObject.

harlowja found that in python 3.4, if an object is None or "a string" or something other than an oslo_versionedobject and it is compared to an versionedobject, the __eq__ compare method will be called. This will fail because the None.obj_to_primitive() is not a valid attribute.

This was found in a patch http://logs.openstack.org/54/177054/40/check/gate-cinder-python34/5bcd306/console.html#_2015-06-29_16_33_17_810, which failed in python 3.4 but passed in python 2.7. There appears to be some difference on when __eq__ is called and when it is not in python 3.4 vs. 2.7.

Take for example,

class Thingee(object):

  def __eq__(self, obj):
    print 'thingee eq called with %s' % obj
    return False

a = Thingee()
print a == None
print a != None

In python 2.7, the results are:
thingee eq called with None
False
True

In python 3.4, the results are:
thingee eq called with None
False
thingee eq called with None
True

In python 3.4, != calls __eq__.

[Thang Pham (thang-pham)]

Patch available - https://review.openstack.org/206679

[Davanum Srinivas (DIMS) (dims-v)]

This issue was fixed in the openstack/oslo.versionedobjects 1.10.0 release.

[Ben Nemec (bnemec)]

Marking fix released per the last comment.