enable_lazy should be deprecated/removed

[Matt Riedemann]

As seen in a few projects that are implementing the upgrade-checkers command goal for Stein, using the oslo_i18n.enable_lazy() hook causes issues with the upgrade check command output:

http://paste.openstack.org/show/734156/

osboxes@osboxes:~/git/searchlight$ tox -e venv -- searchlight-status upgrade check
venv develop-inst-noop: /home/osboxes/git/searchlight
venv installed: amqp==2.3.2,appdirs==1.4.3,asn1crypto==0.24.0,attrs==18.2.0,Babel==2.6.0,cachetools==2.1.0,certifi==2018.10.15,cffi==1.11.5,chardet==3.0.4,cliff==2.14.0,cmd2==0.9.6,colorama==0.4.0,contextlib2==0.5.5,coverage==4.5.1,cryptography==2.3.1,debtcollector==1.20.0,decorator==4.3.0,dnspython==1.15.0,dogpile.cache==0.6.7,elasticsearch==2.4.1,eventlet==0.24.1,extras==1.0.0,fasteners==0.14.1,fixtures==3.0.0,flake8==2.2.4,future==0.17.1,futurist==1.7.0,greenlet==0.4.15,hacking==0.10.3,httplib2==0.11.3,idna==2.7,iso8601==0.1.12,Jinja2==2.10,jmespath==0.9.3,jsonpatch==1.23,jsonpointer==2.0,jsonschema==2.6.0,keystoneauth1==3.11.1,keystonemiddleware==5.3.0,kombu==4.2.1,linecache2==1.0.0,MarkupSafe==1.0,mccabe==0.2.1,mock==2.0.0,monotonic==1.5,mox3==0.26.0,msgpack==0.5.6,munch==2.3.2,netaddr==0.7.19,netifaces==0.10.7,openstacksdk==0.19.0,os-client-config==1.31.2,os-service-types==1.3.0,osc-lib==1.11.1,oslo.cache==1.31.1,oslo.concurrency==3.28.1,oslo.config==6.6.2,oslo.context==2.21.0,oslo.i18n==3.22.1,oslo.log==3.40.1,oslo.messaging==9.1.1,oslo.middleware==3.36.0,oslo.policy==1.40.1,oslo.serialization==2.28.1,oslo.service==1.32.0,oslo.upgradecheck==0.1.0,oslo.utils==3.37.1,oslotest==3.7.0,osprofiler==2.5.0,Paste==3.0.3,PasteDeploy==1.5.2,pbr==5.1.0,pep8==1.5.7,prettytable==0.7.2,psutil==5.4.8,pycadf==2.8.0,pycparser==2.19,pyflakes==0.8.1,pyinotify==0.9.6,pyOpenSSL==18.0.0,pyparsing==2.3.0,pyperclip==1.7.0,python-cinderclient==4.1.0,python-dateutil==2.7.5,python-designateclient==2.11.0,python-glanceclient==2.14.0,python-ironicclient==2.5.0,python-keystoneclient==3.18.0,python-mimeparse==1.6.0,python-neutronclient==6.10.0,python-novaclient==11.1.0,python-subunit==1.3.0,python-swiftclient==3.6.0,pytz==2018.7,PyYAML==3.13,repoze.lru==0.7,requests==2.20.0,requestsexceptions==1.4.0,rfc3986==1.1.0,Routes==2.4.1,-e git://git.openstack.org/openstack/searchlight@e9b47947ade21b13c9c8fc14ba42420dbf0707ee#egg=searchlight,simplegeneric==0.8.1,simplejson==3.16.0,six==1.11.0,statsd==3.3.0,stestr==2.1.1,stevedore==1.30.0,testtools==2.3.0,traceback2==1.4.0,unittest2==1.1.0,urllib3==1.24.1,vine==1.1.4,voluptuous==0.11.5,warlock==1.3.0,wcwidth==0.1.7,WebOb==1.8.3,wrapt==1.10.11,WSME==0.9.3
venv runtests: PYTHONHASHSEED='1392988093'
venv runtests: commands[0] | searchlight-status upgrade check
Error:
Traceback (most recent call last):
  File "/home/osboxes/git/searchlight/.tox/venv/lib/python3.5/site-packages/oslo_upgradecheck/upgradecheck.py", line 184, in main
    return conf.command.action_fn()
  File "/home/osboxes/git/searchlight/.tox/venv/lib/python3.5/site-packages/oslo_upgradecheck/upgradecheck.py", line 134, in check
    print(t)
  File "/home/osboxes/git/searchlight/.tox/venv/lib/python3.5/site-packages/prettytable.py", line 237, in __str__
    return self.__unicode__()
  File "/home/osboxes/git/searchlight/.tox/venv/lib/python3.5/site-packages/prettytable.py", line 243, in __unicode__
    return self.get_string()
  File "/home/osboxes/git/searchlight/.tox/venv/lib/python3.5/site-packages/prettytable.py", line 995, in get_string
    lines.append(self._stringify_header(options))
  File "/home/osboxes/git/searchlight/.tox/venv/lib/python3.5/site-packages/prettytable.py", line 1066, in _stringify_header
    bits.append(" " * lpad + self._justify(fieldname, width, self._align[field]) + " " * rpad)
  File "/home/osboxes/git/searchlight/.tox/venv/lib/python3.5/site-packages/prettytable.py", line 187, in _justify
    return text + excess * " "
  File "/home/osboxes/git/searchlight/.tox/venv/lib/python3.5/site-packages/oslo_i18n/_message.py", line 230, in __add__
    raise TypeError(msg)
TypeError: Message objects do not support addition.

The lazy translation effort from IBM was abandoned several years ago and these "big tent" projects are probably just still calling this code because it was copied from nova or glance originally, but that's all been removed from the core projects (or should have been by now). Anyway, it causes issues and isn't supported, so we should work to deprecate and remove the enable_lazy translation code from oslo.i18n.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/615610

[Ben Nemec (bnemec)]

For posterity, here's the gist of our IRC discussion about this:

Nobody had any objections to deprecating this functionality, although we should probably socialize that discussion further. Since we can't do a deprecation and removal within this cycle, we are going to fix the problem in oslo.upgradecheck to unblock that work. We can then pursue the oslo.i18n deprecation in a less urgent manner.

[Matt Riedemann (mriedem)]

Email to the ops, sigs and dev lists:

http://lists.openstack.org/pipermail/openstack-operators/2018-November/016139.html

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/615610
Committed: https://git.openstack.org/cgit/openstack/oslo.upgradecheck/commit/?id=c4283dd0ebbb2e64947b966e51b7f3f47233b7be
Submitter: Zuul
Branch: master

commit c4283dd0ebbb2e64947b966e51b7f3f47233b7be
Author: Ben Nemec <email address hidden>
Date: Mon Nov 5 17:09:58 2018 +0000

    Force translation of table header

    Concatenation of lazily translated strings using + is not supported,
    but prettytable is doing that internally with one of the translated
    strings that we pass in. Use six.text_type to force immediate
    translation of the string before passing it to prettytable.

    Change-Id: I73929f9df85a9856bb70b37ee08f5399f98fdb00
    Closes-Bug: 1801761

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/oslo.upgradecheck 0.1.1 release.

[Luigi Toscano (ltoscano)]

I just noticed that we (Sahara) use it. Is there a suggested path for migrating out of it?

[Ben Nemec (bnemec)]

You can stop using it today by just removing the enable_lazy call(s) from your code. That will cause oslo.i18n to use the regular translation code internally instead of the lazy framework.