I had the same problem, the git protocol is blocked in my testing environment.
The solution is to modify the sourcerc file in the devstack installation folder to use https instead of git. You have to look for that line and change it. This file is also known as the local.conf file.
Default setting in sourcerc file:
GIT_BASE=${GIT_BASE:-git://git.openstack.org}
Modified setting that should bypass git restrictions:
GIT_BASE=${GIT_BASE:-https://git.openstack.org}
Simply add this modified line to the local/localrc section of your local.conf file in the DevStack directory and it should use the HTTPS protocol instead of the Git protocol! More info on the local.conf file here - http://devstack.org/configuration.html