Internationalization
====================

Nova uses the `oslo.i18n library
<http://docs.openstack.org/developer/oslo.i18n/index.html>`_ to support
internationalization. The oslo.i18n library is built on top of `gettext
<http://docs.python.org/library/gettext.html>`_ and provides functions that are
used to enable user-facing strings such as log messages to appear in the
appropriate language in different locales.

Nova exposes the oslo.i18n library support via the ``nova/i18n.py`` integration
module. This module provides the functions needed to wrap translatable strings.
It provides the ``_()`` wrapper for general user-facing messages (such
as ones that end up in command line responses, or responses over the
network).

One upon a time there was an effort to translate log messages in
OpenStack projects. But starting with the Ocata release these are no
longer being supported. Log messages **should not** be translated. Any
use of ``_LI()``, ``_LW()``, ``_LE()``, ``_LC()`` are vestigial and
will be removed over time. No new uses of these should be added.

You should use the basic wrapper ``_()`` for strings which are not log
messages that are expected to get to an end user::

    raise nova.SomeException(_('Invalid service catalogue'))

Do not use ``locals()`` for formatting messages because:
1. It is not as clear as using explicit dicts.
2. It could produce hidden errors during refactoring.
3. Changing the name of a variable causes a change in the message.
4. It creates a lot of otherwise unused variables.

If you do not follow the project conventions, your code may cause hacking
checks to fail.

The ``_()`` function can be imported with ::

    from nova.i18n import _
