Eliminate default value as a mutable object

[hongbin]

The default value is evaluated only once. This makes a difference when the default is a mutable object such as a list, dictionary, or instances of most classes. Magnum should follow what Python suggests: Do not to use mutable object as a default value.

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/198465
Committed: https://git.openstack.org/cgit/openstack/magnum/commit/?id=0b9b7de79ab96181e7ce89d0dd4cf3e183aff9de
Submitter: Jenkins
Branch: master

commit 0b9b7de79ab96181e7ce89d0dd4cf3e183aff9de
Author: Hongbin Lu <email address hidden>
Date: Fri Jul 3 18:09:28 2015 -0400

    Eliminate mutable default arguments

    The best practice in Python is not to use mutable object (i.e. list,
    dictionary, or instances of most classes) as value of default argument.

    See: https://docs.python.org/2/tutorial/controlflow.html#default-argument-values

    This patch also added a hacking rule to enforce this practice.

    Change-Id: I4aa8aede57d6fd31b4b30c3f7535b819e591165d
    Closes-Bug: 1471349

[Timur Sufiev (tsufiev-x)]

I find this check highly valuable and think it could be generalized for other OpenStack projects as well. Particularly, for Horizon.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/225613

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/225613
Committed: https://git.openstack.org/cgit/openstack/horizon/commit/?id=7023050eddc9b2361bd200309329e4e6bf89709d
Submitter: Jenkins
Branch: master

commit 7023050eddc9b2361bd200309329e4e6bf89709d
Author: Timur Sufiev <email address hidden>
Date: Mon Sep 21 13:22:59 2015 +0300

    Eliminate mutable default arguments

    The best practice in Python is not to use mutable object (i.e. list,
    dictionary, or instances of most classes) as value of default
    argument (see https://goo.gl/Kwhg0T). A hacking rule to enforce this
    practice is added as well.

    The patch was inspired by CR https://review.openstack.org/#/c/198465/
    and took most of its code from it as well. That's why original
    copyrights are kept.

    Closes-Bug: #1471349
    Change-Id: Ia77b1736dbc3d4e28ff2d2c3424e9cfcaefa5077

[Doug Hellmann (doug-hellmann)]

This issue was fixed in the openstack/horizon 9.0.0.0b2 development milestone.