mistral tests fail with Tenacity >= 8.0.1

[Thomas Goirand]

Hi,

As per the Debian bug report at: https://bugs.debian.org/1005467 Mistral fails at least in its unit tests, and probably functionally as well, with this type of error:

> File "/<<PKGBUILDDIR>>/mistral/db/utils.py", line 109, in decorate
> return retry.call(_with_auth_context, auth_ctx, func, *args, **kw)
> AttributeError: 'Retrying' object has no attribute 'call'

The bug report in Debian shows 420 instances of the same crash.

Please help me to fix the upstream Mistral code and the downstream Debian package. I prefer if we can move forward and fix the Tenacity >= 8.x.x compat rather than declaring incompatibility and pinning, since python3-tenacity in Debian is already in version 8.x.