cinder requirements.txt includes oslo.vmware. The olso_vmware module is referenced in a few of the volume/drivers/vmware files (and tests), but our policy is to then list this in test-requirements.txt and as an extra in setup.cfg, not in requirements.txt, so that setups which are not using the vmware drivers are not forced to install vmware-specific modules.
This was originally fixed under https://bugs.launchpad.net/cinder/+bug/1475739 with https://github.com/openstack/cinder/commit/e67adc385ce6997249fbf70e9402264f758fc6f4 and https://github.com/openstack/cinder/commit/478e8e970e54aaf3a034dc6347605c1b18291d0d , but then both of those patches were later reverted under https://github.com/openstack/cinder/commit/6da01c1b4102b36314b96ad73ec38a3fdec1355b. We need to get those put back, which may or may not require changing the min tox version to 1.7 from 1.6 (see https://review.openstack.org/#/c/211614/). It's not clear from the comments why that patch was abandoned in Liberty, but it should be revived for Mitaka. Or there may be another way to make the tox.ini changes that will work for 1.6, if we fail to move that up to 1.7.
tox version is now 1.8 for cinder. Will update with initial changes from 1475739