Adds os-win dependency spec

https://blueprints.launchpad.net/nova/+spec/add-os-win-library

Hyper-V is involved in many of OpenStack components (nova, neutron,
cinder, ceilometer, etc.) and will be involved with other components
in the future.

A common library can be created in order to reduce the code duplication
between all these components (utils classes, which interacts directly
with Hyper-V through WMI), making it easier to maintain, review and
propose new changes to current and future components.

Change-Id: I55a702557bbc827f01d45870f80de88fe07a9148
Implements: blueprint add-os-win-library

specs/mitaka/approved/add-os-win-library.rst

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+..
+ This work is licensed under a Creative Commons Attribution 3.0 Unported
+ License.
+
+ http://creativecommons.org/licenses/by/3.0/legalcode
+
+=====================
+Add os-win dependency
+=====================
+
+https://blueprints.launchpad.net/nova/+spec/add-os-win-library
+
+Hyper-V is involved in many of OpenStack components (nova, neutron, cinder,
+ceilometer, etc.) and will be involved with other components in the future.
+
+A common library has been created, named os-win, in order to reduce the code
+duplication between all these components (utils classes, which interacts
+directly with Hyper-V through WMI), making it easier to maintain, review and
+propose new changes to current and future components.
+
+Problem description
+===================
+
+There are many Hyper-V utils modules duplicated across several projects,
+which can be refactored into os-win, reducing the code duplication and making
+it easier to maintain. Plus, the review process will be simplified, as
+reviewers won't have to review Hyper-V related code, in which not everyone is
+proficient.
+
+Use Cases
+---------
+
+This blueprint impacts Developers and Reviewers.
+
+Developers will be able to submit Hyper-V related commits directly to os-win.
+
+Reviewers will not have to review low level Hyper-V related code. Thus, the
+amount of code that needs to be reviewed will be reduced by approximately 50%.
+
+Proposed change
+===============
+
+In order to implement this blueprint, minimal changes are necessary, as the
+behaviour will stay the same.
+
+The primary changes that needs to be done on nova are as follows:
+
+* add os-win in requirements.txt
+* replace ``nova.virt.hyperv.vmutils.HyperVException`` references to
+  ``os_win.HyperVException``
+* replace all ``nova.virt.hyperv.utilsfactory`` imports used by the
+  `HyperVDriver` with ``os_win.utilsfactory``
+* remove all utils modules and their unit tests in ``nova.virt.hyperv``, since
+  they will no longer be used.
+* other trivial changes, which are to be seen in the implementation.
+
+Changes that needs to be done on other projects:
+
+* add os-win in global-requirements.txt [1]
+
+Alternatives
+------------
+
+Originally, os-win was planned to be part of Oslo, it was suggested that os-win
+should be a standalone project, as otherwise the Oslo team would also have to
+maintain in and there aren't many / anyone that specializes in Windows /
+Hyper-V related code.
+
+Data model impact
+-----------------
+
+None
+
+REST API impact
+---------------
+
+None
+
+Security impact
+---------------
+
+None
+
+Notifications impact
+--------------------
+
+None
+
+Other end user impact
+---------------------
+
+None
+
+Performance Impact
+------------------
+
+None
+
+Other deployer impact
+---------------------
+
+os-win dependency will have to be installed in order for the HyperVDriver to be
+used.
+
+Developer impact
+----------------
+
+In a typical scenario, a blueprint implementation for the Hyper-V Driver will
+require 2 parts:
+
+* os-win commit, adding Hyper-V related utils required in order to implement
+  the blueprint.
+* nova commit, implementing the blueprint and using the changes made in os-win.
+
+If a nova commit requires a newer version of os-win, the patch to
+global-requirements should be referenced with Depends-On in the commit message.
+
+For bugfixes, there are chances that they require 2 patches: one for nova and
+one for os-win. The backported bugfix must be a squashed version of the 2
+patches, referencing both commit IDs in the commit message::
+
+    (cherry picked from commit <nova-commit-id>)
+    (cherry picked from commit <os-win-commit-id)
+
+If the bugfix requires only one patch to either project, backporting will
+proceed as before.
+
+Implementation
+==============
+
+Assignee(s)
+-----------
+
+Primary assignee:
+  Claudiu Belu <cbelu@cloudbasesolutions.com>
+
+Other contributors:
+  Lucian Petrut <lpetrut@cloudbasesolutions.com>
+
+Work Items
+----------
+
+As described in the `Proposed change` section.
+
+Dependencies
+============
+
+Adds os-win library as a dependency.
+
+Testing
+=======
+
+* Unit tests
+* Hyper-V CI
+
+Documentation Impact
+====================
+
+The Hyper-V documentation page [3] will have to be updated to include os-win
+as a dependency.
+
+References
+==========
+
+[1] os-win added to global-requirements.txt:
+        https://review.openstack.org/#/c/230394/
+
+[2] os-win repository:
+        https://github.com/openstack/os-win
+
+[3] Hyper-V virtualization platform documentation page:
+        http://docs.openstack.org/liberty/config-reference/content/hyper-v-virtualization-platform.html
+
+History
+=======
+
+Mitaka: Introduced