Make oslo.i18n an optional dependency

In an ideal world we would have all messages translated to at least major
languages. In reality, ironic has never boasted a great set of translation,
and according to Zanata only 2.94% of messages are translated for ironic
in Train (1.33% for ironic-inspector). Given that ironic-python-agent is
not translated at all, using i18n by default seems an overkill.

Change-Id: I12287c6b7208af487cc9eee825ae7f38ec707d91

ironic/api/wsgi.py

@@ -14,10 +14,10 @@
 import sys
 
 from oslo_config import cfg
-import oslo_i18n as i18n
 from oslo_log import log
 
 from ironic.api import app
+from ironic.common import i18n
 from ironic.common import service
 
 

ironic/cmd/__init__.py

@@ -25,6 +25,6 @@ import eventlet
 
 eventlet.monkey_patch(os=False)
 
-import oslo_i18n as i18n  # noqa for I202 due to 'import eventlet' above
+from ironic.common import i18n  # noqa for I202 due to 'import eventlet' above
 
 i18n.install('ironic')

ironic/common/i18n.py

@@ -19,9 +19,20 @@ See https://docs.openstack.org/oslo.i18n/latest/user/
 
 """
 
-import oslo_i18n as i18n
+try:
+    import oslo_i18n as i18n
+except ImportError:
+    def _(msg):
+        return msg
 
-_translators = i18n.TranslatorFactory(domain='ironic')
+    def install(domain):
+        # NOTE(dtantsur): this is called before logging is initialized, so we
+        # cannot really log a warning here.
+        pass
+else:
+    _translators = i18n.TranslatorFactory(domain='ironic')
 
-# The primary translation function using the well-known name "_"
-_ = _translators.primary
+    # The primary translation function using the well-known name "_"
+    _ = _translators.primary
+
+    install = i18n.install

releasenotes/notes/oslo-i18n-optional-76bab4d2697c6f94.yaml

@@ -0,0 +1,5 @@
+---
+upgrade:
+  - |
+    The dependency on ``oslo.i18n`` is now optional. If you would like messages
+    from ironic to be translated, you need to install it explicitly.

requirements.txt

@@ -21,7 +21,6 @@ oslo.config>=5.2.0 # Apache-2.0
 oslo.context>=2.19.2 # Apache-2.0
 oslo.db>=4.40.0 # Apache-2.0
 oslo.rootwrap>=5.8.0 # Apache-2.0
-oslo.i18n>=3.15.3 # Apache-2.0
 oslo.log>=3.36.0 # Apache-2.0
 oslo.middleware>=3.31.0 # Apache-2.0
 oslo.policy>=1.30.0 # Apache-2.0

setup.cfg

@@ -200,3 +200,5 @@ universal = 1
 [extras]
 guru_meditation_reports =
   oslo.reports>=1.18.0 # Apache-2.0
+i18n =
+  oslo.i18n>=3.15.3 # Apache-2.0