Specify http_client interface via an abstract class
Specify http_client interface via an abstract class

Good to have this spelled out explicitly, especially for when we start
adding other non-trivial backends, e.g. keystone, which does a few
things differently from the requests library.

CCI-MOC/haas,henn/hil_sahil,SahilTikale/haas,kylehogan/hil,meng-sun/hil,henn/hil,meng-sun/hil,kylehogan/hil,henn/hil_sahil,henn/haas,henn/hil,kylehogan/haas