AttributeError: NullTranslationsBabel instance has no attribute 'isactive'

[adminusername]

How to Reproduce

While doing a GET operation on /admin/general/plugin, Trac issued an internal error.

(please provide additional details here)

Request parameters:

{'cat_id': u'general', 'panel_id': u'plugin', 'path_info': None}

User agent: Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/47.0.2526.111 Safari/537.36

System Information

Trac	1.0.1
Babel	1.3
Docutils	0.11
Genshi	0.7 (with speedups)
mod_python	3.3.1
Pygments	1.6
pysqlite	2.6.0
Python	2.7.6 (default, Jun 22 2015, 18:01:27) [GCC 4.8.2]
pytz	2012c
RPC	1.1.5
setuptools	3.3
SQLite	3.8.2
Subversion	1.8.8 (r1568071)
jQuery	1.7.2

Enabled Plugins

TestManager	1.9.0
TracAccountManager	0.4.4
TracGenericClass	1.1.6
TracGenericWorkflow	1.0.5
TracXMLRPC	1.1.5

Python Traceback

Traceback (most recent call last):
  File "/usr/lib/python2.7/dist-packages/trac/web/main.py", line 497, in _dispatch_request
    dispatcher.dispatch(req)
  File "/usr/lib/python2.7/dist-packages/trac/web/main.py", line 179, in dispatch
    chosen_handler)
  File "/usr/lib/python2.7/dist-packages/trac/web/main.py", line 325, in _pre_process_request
    chosen_handler = filter_.pre_process_request(req, chosen_handler)
  File "/usr/lib/python2.7/dist-packages/trac/versioncontrol/api.py", line 340, in pre_process_request
    if is_default(reponame):
  File "/usr/lib/python2.7/dist-packages/trac/versioncontrol/api.py", line 34, in is_default
    return not reponame or reponame in ('(default)', _('(default)'))
  File "/usr/lib/python2.7/dist-packages/trac/util/translation.py", line 195, in gettext
    if not self.isactive:
  File "/usr/lib/python2.7/dist-packages/trac/util/translation.py", line 190, in __getattr__
    return getattr(self.active, name)
AttributeError: NullTranslationsBabel instance has no attribute 'isactive'

[Jun Omae]

One of Most frequent duplicates. Try to upgrade to Trac 1.0.2+ otherwise downgrade to Babel 0.9.6.

Also, please search duplicates before submitting new ticket.