cinder db online_db_migration crashes

[Jean-Philippe Evrard]

When doing cinder db online_db_migration I get the following:

2017-10-16 10:35:01.092 5166 CRITICAL cinder [req-f268ff7f-27d3-40fe-9643-f82a0c9b70d8 - - - - -] Unhandled error: TypeError: Message objects do not support addition.
2017-10-16 10:35:01.092 5166 ERROR cinder Traceback (most recent call last):
2017-10-16 10:35:01.092 5166 ERROR cinder File "/openstack/venvs/cinder-master/bin/cinder-manage", line 11, in <module>
2017-10-16 10:35:01.092 5166 ERROR cinder sys.exit(main())
2017-10-16 10:35:01.092 5166 ERROR cinder File "/openstack/venvs/cinder-master/lib/python2.7/site-packages/cinder/cmd/manage.py", line 816, in main
2017-10-16 10:35:01.092 5166 ERROR cinder fn(**fn_kwargs)
2017-10-16 10:35:01.092 5166 ERROR cinder File "/openstack/venvs/cinder-master/lib/python2.7/site-packages/cinder/cmd/manage.py", line 325, in online_data_migrations
2017-10-16 10:35:01.092 5166 ERROR cinder print(t)
2017-10-16 10:35:01.092 5166 ERROR cinder File "/openstack/venvs/cinder-master/lib/python2.7/site-packages/prettytable.py", line 240, in __str__
2017-10-16 10:35:01.092 5166 ERROR cinder return self.__unicode__().encode(self.encoding)
2017-10-16 10:35:01.092 5166 ERROR cinder File "/openstack/venvs/cinder-master/lib/python2.7/site-packages/prettytable.py", line 243, in __unicode__
2017-10-16 10:35:01.092 5166 ERROR cinder return self.get_string()
2017-10-16 10:35:01.092 5166 ERROR cinder File "/openstack/venvs/cinder-master/lib/python2.7/site-packages/prettytable.py", line 995, in get_string
2017-10-16 10:35:01.092 5166 ERROR cinder lines.append(self._stringify_header(options))
2017-10-16 10:35:01.092 5166 ERROR cinder File "/openstack/venvs/cinder-master/lib/python2.7/site-packages/prettytable.py", line 1066, in _stringify_header
2017-10-16 10:35:01.092 5166 ERROR cinder bits.append(" " * lpad + self._justify(fieldname, width, self._align[field]) + " " * rpad)
2017-10-16 10:35:01.092 5166 ERROR cinder File "/openstack/venvs/cinder-master/lib/python2.7/site-packages/prettytable.py", line 203, in _justify
2017-10-16 10:35:01.092 5166 ERROR cinder return (excess//2)*" " + text + (excess//2)*" "
2017-10-16 10:35:01.092 5166 ERROR cinder File "/openstack/venvs/cinder-master/lib/python2.7/site-packages/oslo_i18n/_message.py", line 233, in __radd__
2017-10-16 10:35:01.092 5166 ERROR cinder return self.__add__(other)
2017-10-16 10:35:01.092 5166 ERROR cinder File "/openstack/venvs/cinder-master/lib/python2.7/site-packages/oslo_i18n/_message.py", line 230, in __add__
2017-10-16 10:35:01.092 5166 ERROR cinder raise TypeError(msg)
2017-10-16 10:35:01.092 5166 ERROR cinder TypeError: Message objects do not support addition.
2017-10-16 10:35:01.092 5166 ERROR cinder

It looks like it's an issue with pretty table and our translated headers under python2.7.
I am running this version of cinder (master):
914f5bde72c82bf1e50a09c8cc776e86903c3e86

The version of prettytable is the following:
prettytable==0.7.2
You can see my full list of requirements in my venv in attachment.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/512259

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/512259
Committed: https://git.openstack.org/cgit/openstack/cinder/commit/?id=04543abedd429101dc6b410090e463358d22ca48
Submitter: Zuul
Branch: master

commit 04543abedd429101dc6b410090e463358d22ca48
Author: Jean-Philippe Evrard <email address hidden>
Date: Mon Oct 16 10:36:33 2017 +0000

    Make stringify header work under python2.

    This fixes the following issue appearing during
    cinder-manage db online_data_migrations.

    Change-Id: Ic47f04e06b886656c9a0f0f7a0494a10fef93e80
    Closes-Bug: #1723922

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/cinder 12.0.0.0b1 development milestone.