Fix futurist version conflict

[blag]

So, first off, here's the entire output of the pipconflictchecker command:

--------------------------------------------------
 Conflicts Detected
--------------------------------------------------
 - futurist(1.10.0) openstacksdk(>=2.1.0)

Before reading on, can you tell me what the exact problem is? No StackStorm components rely directly on either futurist or openstacksdk, so where are those dependencies coming from and why are they conflicting?

I couldn't figure it out from this output. I'll circle back around to this point in a bit.

---

This PR fixes the build failures caused by some transitive dependencies dropping support for Python 3.

In this case:

• python-mistralclient depended on
  • osc-lib >= 1.8.0 (resolved to 2.0.0) which depended on
    • openstacksdk >= 0.15.0 (resolved to 0.44.0) which depended on
      • futurist >= 2.1.0 which does not support for Python 2

The latest version of futurist that supports Python 2 is version 1.10.0.

So, to fix the transitive dependency, I explicitly specify a direct dependency of opensacksdk < 0.44.0 for st2actions and st2api. This installs:

• python-mistralclient
  • osc-lib version 2.0.0
    • openstacksdk version 0.43.0
      • futurist version 1.10.0

So that we don't break Python 2 support.

Please note that I am not a fan of this solution, it is simply the best of a few bad options. We cannot track and pin every transitive dependency like this - that's time consuming and unsustainable. This is a temporary solution and once we ship ST2 v3.2 and drop Python 2.7 support we won't need to track transitive dependencies like this as they remove support for Python 2.7.

---

Okay. Let's talk about the output of pipconflictchecker. It's pretty much useless unless you already know exactly what you're looking at, which I do not. Neither futurist nor openstacksdk appear in any of our requirements.txt files - they're both transitive dependencies - so it's exceedingly difficult to figure out what direct requirement/s need to be fixed, and pip-conflict-checker does absolutely nothing to give you any hints.

Instead of using pip-conflict-checker, I just used pip-compile from the pip-tools package. The output of that is illuminating. Here is the complete output of pip-compile when our dependencies have conflicts:

Could not find a version that matches futurist>=1.2.0,>=2.1.0 (from tooz==1.66.1->-r req.txt (line 64))
Tried: 0.1.0, 0.1.0, 0.1.1, 0.1.1, 0.1.2, 0.1.2, 0.2.0, 0.2.0, 0.3.0, 0.3.0, 0.4.0, 0.4.0, 0.5.0, 0.5.0, 0.6.0, 0.6.0, 0.7.0, 0.7.0, 0.8.0, 0.8.0, 0.9.0, 0.9.0, 0.10.0, 0.10.0, 0.11.0, 0.11.0, 0.12.0, 0.12.0, 0.13.0, 0.13.0, 0.14.0, 0.14.0, 0.15.0, 0.15.0, 0.16.0, 0.16.0, 0.17.0, 0.17.0, 0.18.0, 0.18.0, 0.19.0, 0.19.0, 0.20.0, 0.20.0, 0.21.0, 0.21.0, 0.21.1, 0.21.1, 0.22.0, 0.22.0, 0.23.0, 0.23.0, 1.0.0, 1.0.0, 1.1.0, 1.1.0, 1.2.0, 1.2.0, 1.3.0, 1.3.0, 1.3.1, 1.3.1, 1.3.2, 1.3.2, 1.4.0, 1.4.0, 1.5.0, 1.5.0, 1.6.0, 1.6.0, 1.7.0, 1.7.0, 1.8.0, 1.8.0, 1.8.1, 1.8.1, 1.9.0, 1.9.0, 1.10.0, 1.10.0
There are incompatible versions in the resolved dependencies:
  futurist>=1.2.0 (from tooz==1.66.1->-r req.txt (line 64))
  futurist>=2.1.0 (from openstacksdk==0.44.0->osc-lib==2.0.0->python-mistralclient->-r req.txt (line 19))

(The 2.1.0 release of futurist is not shown because that version indicates non-support for Python 2, and this is installing in a Python 2 environment, so pip doesn't even consider installing it.)

From that output, I can tell exactly what packages depend on futurist, and I can tell exactly what file and what line I need to modify.

I updated the Makefile and test-requirements.txt to use pip-compile instead of pip-conflict-checker since the output is so much more helpful.

Once I fix the dependency conflicts, the output of pip-compile is much better (this is only the relevant snippets of the full output):

# ...
futures==3.3.0            # via -r req.txt, apscheduler, futurist, openstacksdk, tenacity, tooz
futurist==1.10.0          # via -r req.txt, tooz
# ...
openstacksdk==0.43.0      # via -r req.txt, osc-lib
# ...
osc-lib==2.0.0            # via -r req.txt, python-mistralclient
# ...
git+https://github.com/StackStorm/python-mistralclient.git#egg=python-mistralclient  # via -r req.txt
# ...
tooz==1.66.1              # via -r req.txt
# ...
# The following packages are considered to be unsafe in a requirements file:
# setuptools

Now, this is a little weird, because openstacksdk version 0.43.0 only depends on the futures package, not the futurist package. But whatever, this fixes the build. And version 0.44.0 of openstacksdk only depends on the futurist package.

Lastly, I add a .git to the python-mistralclient dependency in st2actions/in-requirements.txt to ensure that the dependency only shows up once when combined, sorted, and uniquified with the other requirements.txt files in the Makefile.

[m4dcoder]

LGTM

[blag]

Updating to setuptools >= 42.0 in #4895 fixed this properly. Closing.