centos-binary-cloudkitty-api:train-centos8 broken (probably train and ussuri too)

[Pierre Riteau]

CloudKitty became timezone-aware in Train: https://review.opendev.org/#/c/669192/
The code references tz.UTC from dateutil. However, this was added only in dateutil 2.7.0, while train-centos8 images use package python3-dateutil-2.6.1-6.el8.noarch.

The train CentOS 7 image (even older dateutil version) and the ussuri image are probably broken in a similar way.

Resulting backtrace in cloudkitty-api.log:

2020-07-22 16:33:11.207 26 ERROR wsme.api [req-3c49884a-1412-42bb-a57e-e7c731360148 ef450a969a2945928d3ade785eaae860 19df0f36ede14c29be9ca476222f8ba9 default - -] Server-side error:
 "module 'dateutil.tz' has no attribute 'UTC'". Detail:
Traceback (most recent call last):

  File "/usr/lib/python3.6/site-packages/wsmeext/pecan.py", line 85, in callfunction
    result = f(self, *args, **kwargs)

  File "/usr/lib/python3.6/site-packages/cloudkitty/api/v1/controllers/storage.py", line 71, in get_all
    paginate=False)

  File "/usr/lib/python3.6/site-packages/cloudkitty/storage/v2/influx.py", line 311, in retrieve
    begin, end = self._check_begin_end(begin, end)

  File "/usr/lib/python3.6/site-packages/cloudkitty/storage/v2/influx.py", line 271, in _check_begin_end
    end = tzutils.get_next_month()

  File "/usr/lib/python3.6/site-packages/cloudkitty/tzutils.py", line 150, in get_next_month
    return add_delta(start, datetime.timedelta(days=month_days))

  File "/usr/lib/python3.6/site-packages/cloudkitty/tzutils.py", line 104, in add_delta
    return utc_to_local(local_to_utc(dt, naive=True) + delta)

  File "/usr/lib/python3.6/site-packages/cloudkitty/tzutils.py", line 52, in local_to_utc
    output = dt.astimezone(tz.UTC)

AttributeError: module 'dateutil.tz' has no attribute 'UTC'

[Pierre Riteau (priteau)]

This bug was fixed during the Victoria development cycle in CloudKitty itself with change https://review.opendev.org/c/openstack/cloudkitty/+/747057.

The fix was backported to Ussuri (from 12.1.0) and Train (from 11.1.0).