pyrax dependencies not compatible w/ st2 3.4+

[cognifloyd]

In st2 3.4, we increased the version of oslo.utils to <5.0,>=4.0.0: StackStorm/st2#5121
oslo.utils 4.x requires pbr!=2.1.0,>=2.0.0 (as does stevedore==1.30.1)

However, this pack depends on pyrax>=1.9.3,<2.0. The newest version that matches, pyrax-1.10.0 requires python-novaclient==2.27.0 which requires pbr<2.0,>=1.6 and oslo.utils>=2.0.0. That pbr requirement is not compatible with oslo.utils 4.x.

in st2 3.5, we also started pinning prettytable==2.1.0 in StackStorm/st2#5177
That conlicts directly with python-novaclientn==2.27.0's requirement: PrettyTable<0.8,>=0.7

So, pip cycles for awhile and tries to downgrade pbr, several of the oslo packages, prettytable, and a few other things. Doing that breaks registering the runners, so all the tests blow up.

Icing on the cake, pyrax is unmaintained and version 1.10.0 was the last release:

DEPRECATED: Pyrax is no longer being developed or supported. See openstacksdk and the rackspacesdk plugin in order to interact with Rackspace’s OpenStack-based public cloud.

So, this pack needs to be reworked using maintained libraries.

pyrax is only imported directly by one file, so hopefully it will not be too hard to swap pyrax out for something else.