openstack client (3.6.0 from pip install) is significantly slower than nova client

Hi

I installed python-openstackclient and python-novaclient from pip. I have noticed when I run "openstack server list --all-projects"(3mins and 32 sec) is significantly slower than "nova list --all-tenants" (19sec)

(OS) ➜ ~ time nova list --all-tenants
nova list --all-tenants 1.10s user 0.12s system 6% cpu 19.614 total

(OS) ➜ ~ time openstack server list --all-projects
openstack server list --all-projects 5.75s user 0.48s system 2% cpu 3:32.60 total

Environment
python-openstackclient version:
python-novaclient version:
python version:
OS: OSX

I have compared it with my Ubuntu Xenial desktop which has python-openstackclient (and python-novaclient) installed from ubuntu archive repo and it is much faster and comparable with python-novaclient

➜ ~ time openstack server list --all-projects
openstack server list --all-projects 0.68s user 0.08s system 4% cpu 18.477 total

Desktop environment
➜ ~ openstack --version
openstack 2.3.0
➜ ~ apt-cache policy python-openstackclient
python-openstackclient:
  Installed: 2.3.0-2
  Candidate: 2.3.0-2
  Version table:
 *** 2.3.0-2 500
        500 http://au.archive.ubuntu.com/ubuntu xenial/main amd64 Packages