ryu 3.29 incompatible with oslo.config

[Bob Ball]

ryu 3.29 explicitly prevents compatability with oslo.config 3.2 to preserve python 2.6 compatability for ryu:
https://github.com/osrg/ryu/commit/1ed92b25b5997f804dd70a4f072fd20f6af618e0

Global-requirements now requires oslo.config 3.2:
https://github.com/openstack/requirements/blob/master/global-requirements.txt

Citrix's internal Neutron CI shows the breakage when ryu 3.29 is used (latest known good version was 3.26):
2016-01-07 07:34:56.673 ERROR neutron.plugins.ml2.drivers.openvswitch.agent.ovs_neutron_agent Exit code: 1; Stdin: ; Stdout: ; Stderr: Traceback (most recent call last):
  File "/usr/local/bin/neutron-rootwrap-xen-dom0", line 4, in <module>
    __import__('pkg_resources').require('neutron==8.0.0.0b2.dev265')
  File "/usr/local/lib/python2.7/dist-packages/pkg_resources/__init__.py", line 3138, in <module>
    @_call_aside
  File "/usr/local/lib/python2.7/dist-packages/pkg_resources/__init__.py", line 3124, in _call_aside
    f(*args, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/pkg_resources/__init__.py", line 3151, in _initialize_master_working_set
    working_set = WorkingSet._build_master()
  File "/usr/local/lib/python2.7/dist-packages/pkg_resources/__init__.py", line 663, in _build_master
    return cls._build_from_requirements(__requires__)
  File "/usr/local/lib/python2.7/dist-packages/pkg_resources/__init__.py", line 676, in _build_from_requirements
    dists = ws.resolve(reqs, Environment())
  File "/usr/local/lib/python2.7/dist-packages/pkg_resources/__init__.py", line 854, in resolve
    raise VersionConflict(dist, req).with_context(dependent_req)
pkg_resources.ContextualVersionConflict: (oslo.config 3.2.0 (/usr/local/lib/python2.7/dist-packages), Requirement.parse('oslo.config<=3.0.0,>=1.6.0'), set(['ryu']))
 Agent terminated!

[Armando Migliaccio (armando-migliaccio)]

https://review.openstack.org/#/c/264741

[IWAMOTO Toshihiro (iwamoto)]

It seems to be specific to Citrix CI, as openstack.org's Jenkins aren't affected.

Maybe an environment marker could be used on ryu's pip-requires to mitigate the issue.

[IWAMOTO Toshihiro (iwamoto)]

global-requirements now avoids ryu 3.29. Ryu 3.29.1 has a fix for this.
Is the "Citrix's internal Neutron CI" running fine?