Recibo este error en mi máquina Ubuntu 12.04 con mysql 5.5 después de importar algo de contenido de Wordpress al blog_blogpost de Mezzanine.

ValueError at /admin/blog/blogpost/
Database returned an invalid value in QuerySet.dates(). Are time zone definitions and pytz installed?

Request Method: GET
Request URL:    http://127.0.0.1:8000/admin/blog/blogpost/
Django Version: 1.6.1
Exception Type: ValueError
Exception Value:    
Database returned an invalid value in QuerySet.dates(). Are time zone definitions and pytz installed?
Exception Location: /home/me/.mezenv/local/lib/python2.7/site-packages/django/db/models/sql/compiler.py in results_iter, line 1107
Python Executable:  /home/me/.mezenv/bin/python
Python Version: 2.7.3
Python Path:    
[u'/home/me',
 '/home/me/sai',
 '/home/me/.mezenv/local/lib/python2.7/site-packages/distribute-0.6.24-py2.7.egg',
 '/home/me/.mezenv/local/lib/python2.7/site-packages/pip-1.1-py2.7.egg',
 '/home/me/.mezenv/lib/python2.7',
 '/home/me/.mezenv/lib/python2.7/plat-linux2',
 '/home/me/.mezenv/lib/python2.7/lib-tk',
 '/home/me/.mezenv/lib/python2.7/lib-old',
 '/home/me/.mezenv/lib/python2.7/lib-dynload',
 '/usr/lib/python2.7',
 '/usr/lib/python2.7/plat-linux2',
 '/usr/lib/python2.7/lib-tk',
 '/home/me/.mezenv/local/lib/python2.7/site-packages']
Server time:    Sat, 25 Jan 2014 13:44:11 +0100


Error during template rendering

In template /home/me/.mezenv/local/lib/python2.7/site-packages/grappelli_safe/templates/admin/change_list.html, error at line 140

Agregué a mi local_settings.py

import pytz
from pytz import *

y también la zona horaria definida en my.cnf [mysqld]

default-time-zone = "+01:00"

pero sigo recibiendo el error unitl. Obtengo la línea en la plantilla:

la etiqueta es:

140 {% block date_hierarchy%} {% date_hierarchy cl%} {% endblock%}

Aprecio su ayuda para resolverlo.