Comment 4 for bug 1747575

Reviewed: https://review.openstack.org/541543
Committed: https://git.openstack.org/cgit/openstack/oslo.utils/commit/?id=1e0570b2a598b43a85faa28e07ab97d56bf5ba5e
Submitter: Zuul
Branch: stable/queens

commit 1e0570b2a598b43a85faa28e07ab97d56bf5ba5e
Author: John L. Villalovos <email address hidden>
Date: Mon Feb 5 22:29:38 2018 -0800

    Fix breaking unit tests due to iso8601 changes

    The move from iso8601===0.1.11 to iso8601===0.1.12 broke unit
    tests in oslo.utils.

    iso8601 used to do:
        from datetime import datetime

    But now they call datetime.datetime():
        import datetime
        datetime.datetime()

    Unfortunately the unit tests that mocked datetime.datetime() are now
    mocking the one in iso8601. This causes a failure in the unit tests.

    Fix this by using the 'wraps' argument to mock. So that the calls will
    get passed through to datetime.datetime. Also changed to using the
    decorator style of mock.

    In addition Python 3 unit tests were broken due to changing how the
    UTC time zone is represented from 'UTC' to 'UTC+00:00'.

    Closes-Bug: #1747575
    Closes-Bug: #1744160
    Change-Id: Ia80ffb5e571cc5366bef2bc1a32c457a3c16843d
    (cherry picked from commit 010fe3b1023871740b57dbc450f80e6c0c0f6e43)