Django fandjango migration 4.2
Ok, I get it. The problem was with mysql database. The new version added a json field extradata. MySql interpreted it as text field with NULL value. So the problem was that fandjango wanted empty json, not NULL. I have updated the extradata field with '{}' and it's worked. 
Now I have a standart problem: The mobile version of the app is unavailable because it is misconfigured for mobile access. 
As it was earlier, before new version
Now I will try to figure out what is this.  :)
After migration fandjango to version 4.2., I've got an error when I access my facebook application:
Exception Value: [u'Enter valid JSON']
Exception Location: /usr/local/lib/python2.7/dist-packages/jsonfield/fields.py in pre_init, line 77
Trace: 
/usr/local/lib/python2.7/dist-packages/jsonfield/subclassing.py in set
            obj.dict[self.field.name] = self.field.pre_init(value, obj)
    ...
jsonfield.subclassing.Creator object at 0x2a5c750
obj
User: My User
value u''
/usr/local/lib/python2.7/dist-packages/jsonfield/fields.py in pre_init
                            raise ValidationError(_("Enter valid JSON"))
    ...
▼ Local vars
Variable    Value
self
jsonfield.fields.JSONField: extra_data
obj
User: My User
value   u''
I have upgraded fandjagno using pip install -upgrade fandjango, python manage.py migrate fandjango.
There were another problems:
-No module named jsonfield, so I installed it using pip
-No module named dateutil.tz, so I installed it as well.
-Also it asked for property DJANGO_SITE_URL, which was not defined in the settings object. I putted also it in the settings file. However I didn't find any documentation about this property.
So now I am trying to figure out what else is needed.