Installing mailman-web. Error: There is a version conflict. We already have: pbr 1.8.1 but lockfile 0.11.0 requires 'pbr!=0.7,<1.0,>=0.6'. It looks like lockfile does not actually need a specific version of pbr. https://bugs.launchpad.net/pylockfile/+bug/1506679

not sure though since I manually installed mailman