trac-admin /path upgrade fails with AttributeError: 'NullTranslations' object has no attribute 'add'

[Marius Gedminas]

I've upgraded a server from Ubuntu 12.04 LTS to 14.04 LTS and now I'm trying to upgrade my Trac instances. This fails:

$ trac-admin /opt/zope-trac upgrade
Traceback (most recent call last):
  File "/usr/bin/trac-admin", line 9, in <module>
    load_entry_point('Trac==1.0.1', 'console_scripts', 'trac-admin')()
  File "/usr/lib/python2.7/dist-packages/trac/admin/console.py", line 567, in run
    translation.activate(locale)
  File "/usr/lib/python2.7/dist-packages/trac/util/translation.py", line 325, in activate
    translations.activate(locale, env_path)
  File "/usr/lib/python2.7/dist-packages/trac/util/translation.py", line 152, in activate
    t.add(Translations.load(locale_dir, locale or 'en_US',
AttributeError: 'NullTranslations' object has no attribute 'add'

ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: trac 1.0.1-2
ProcVersionSignature: Ubuntu 3.13.0-85.129-generic 3.13.11-ckt36
Uname: Linux 3.13.0-85-generic x86_64
ApportVersion: 2.14.1-0ubuntu3.19
Architecture: amd64
Date: Wed Apr 27 14:01:51 2016
PackageArchitecture: all
ProcEnviron:
 LC_CTYPE=lt_LT.UTF-8
 TERM=xterm-256color
 PATH=(custom, no user)
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: trac
UpgradeStatus: Upgraded to trusty on 2016-04-27 (0 days ago)

[Marius Gedminas (mgedmin)]

Upstream bug: https://trac.edgewall.org/ticket/11621

Trac 1.0.1 is incompatible with python-babel 1.x (Ubuntu 14.04 LTS ships python-babel 1.3+dfsg.1-2ubuntu2). Trac 1.0.2 has a fix for this.

Upstream fix: https://trac.edgewall.org/changeset/11783.

I think this fix ought to be backported. I'll see if I can manage to propose a SRU.