Requires jsonschema >= 2.4.0 (not 2.2.0)

[James Page]

Detected during kilo-3 updates in Ubuntu vivid (jsonschema 2.3.0):

Traceback (most recent call last):
  File "designate/tests/test_objects/test_base.py", line 368, in test_validate_recursive
    obj.validate()
  File "designate/objects/base.py", line 302, in validate
    errors.append(ValidationError.from_js_error(error))
  File "designate/objects/validation_error.py", line 33, in from_js_error
    e.relative_path = js_error.relative_path
AttributeError: 'ValidationError' object has no attribute 'relative_path'

relative_path was introduced in 2.4.0:

https://github.com/Julian/jsonschema/commit/44b35706a7476fb42ac47520860b63aeebfe39e5

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/167570

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/167570
Committed: https://git.openstack.org/cgit/openstack/designate/commit/?id=2709bd7187c0758c3a2113b5cb8dc6e4cf0d7b82
Submitter: Jenkins
Branch: master

commit 2709bd7187c0758c3a2113b5cb8dc6e4cf0d7b82
Author: Graham Hayes <email address hidden>
Date: Wed Mar 25 11:54:42 2015 +0000

    Remove usage of relative_path in ValidationError Objects

    * 'relative_path' requires JSONSchema 2.4.0
    * Defaults to trying 'relative_path' and falls back to 'path'

    Change-Id: Ie8902a3b943ea4e631155ae208aed9d3911c9767
    Closes-Bug: #1436261