Portable exception to avoid syntax error message

[Hengqing Hu]

Every time I open ansible/library/merge_configs.py, I got the following error:
ansible/library/merge_configs.py|90 col 21 error| invalid syntax

Checking other files, they all use 'as' keyword for exception:
grep -r "except.*as.*" *
docker/kolla-ansible/kolla_keystone_user.py: except Exception as e:
docker/kolla-ansible/kolla_keystone_service.py: except Exception as e:

According to Python 3 Porting guide
http://docs.pythonsprints.com/python3_porting/py-porting.html

Exceptions were changed in a few ways for Python 3. First, strings
are no longer usable as exceptions. Additionally, the raise syntax no
longer accepts comma-separated arguments, instead working with exception
instances. Perhaps the largest difference in Python 3 is that exception
objects are only available via the as keyword, which was introduced in 2.6.

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/218757
Committed: https://git.openstack.org/cgit/stackforge/kolla/commit/?id=1dab839de49be7ef92f274416b417b2007c1d9bd
Submitter: Jenkins
Branch: master

commit 1dab839de49be7ef92f274416b417b2007c1d9bd
Author: Hengqing Hu <email address hidden>
Date: Mon Aug 31 15:58:13 2015 +0800

    Expose exception objects via the as keyword

    According to Python 3 Porting guide
    http://docs.pythonsprints.com/python3_porting/py-porting.html

    Exceptions were changed in a few ways for Python 3. First, strings
    are no longer usable as exceptions. Additionally, the raise syntax no
    longer accepts comma-separated arguments, instead working with exception
    instances. Perhaps the largest difference in Python 3 is that exception
    objects are only available via the as keyword, which was introduced in
    2.6.

    Change-Id: Ide665ecc4b7f14bd58bafab47e05a86a4cf2d141
    Closes-Bug: #1490526