Comment 5 for bug 1446847

pip install 'keystonemiddleware>=1.0.0,<1.4.0' is called directly.
Collecting stevedore>=1.3.0 (from oslo.config>=1.4.0->keystonemiddleware<1.4.0,>=1.0.0)

Then *after* that we call _sync_requirements_file which applies
'stevedore': 'stevedore>=1.0.0,<=1.2.0'

Then we install keystone:
install -e /opt/stack/new/keystone
Which transitively is ok with stevedore
Requirement already satisfied (use --upgrade to upgrade): stevedore>=1.1.0 in /usr/local/lib/python2.7/dist-packages (from python-keystoneclient<1.2.0,>=0.10.0->keystone==2014.2.4.dev2)

And then we lower it - invalidating previously made pip choices (https://github.com/pypa/pip/issues/2687)
pip install -e /opt/stack/new/glance
...
Collecting stevedore<=1.2.0,>=1.0.0 (from glance==2014.2.4.dev1)
2015-04-21 20:16:34.076 | Downloading http://pypi.region-b.geo-1.openstack.org/packages/py2.py3/s/stevedore/stevedore-1.2.0-py2.py3-none-any.whl

Now, we're installing keystonemiddleware from a release (good), but that release strictly requires a newer version of stevedore than Juno is willing to accept.

One possible fix : use an older keystonemiddleware.
Another possible fix, loosen the global requirements for juno to accept newer stevedores - since its API compatible (1.2 ~= 1.4) we should be able to do that.