AssertionError when ISP try to change it's shortname

2017-03-15 18:00:11.200296: Attempting to update <ISP u'FMA'>
    last successful update=2015-11-12 11:00:04.083865+01:00
    last update attempt=2015-11-13 14:00:03.556809+01:00
    next update was scheduled 487 days, 16:00:06.848470 ago
    strike=0
Traceback (most recent call last):
  File "ffdnispdb/cron_task.py", line 151, in <module>
    db.session.commit()
  File "/srv/www/ffdn.org/db/env/local/lib/python2.7/site-packages/sqlalchemy/orm/scoping.py", line 149, in do
    return getattr(self.registry(), name)(*args, **kwargs)
  File "/srv/www/ffdn.org/db/env/local/lib/python2.7/site-packages/sqlalchemy/orm/session.py", line 721, in commit
    self.transaction.commit()
  File "/srv/www/ffdn.org/db/env/local/lib/python2.7/site-packages/sqlalchemy/orm/session.py", line 354, in commit
    self._prepare_impl()
  File "/srv/www/ffdn.org/db/env/local/lib/python2.7/site-packages/sqlalchemy/orm/session.py", line 323, in _prepare_impl
    self.session.dispatch.before_commit(self.session)
  File "/srv/www/ffdn.org/db/env/local/lib/python2.7/site-packages/sqlalchemy/event.py", line 372, in __call__
    fn(*args, **kw)
  File "/srv/www/ffdn.org/db/ffdn-db/ffdnispdb/models.py", line 207, in pre_save_hook
    v.pre_save(sess)
  File "/srv/www/ffdn.org/db/ffdn-db/ffdnispdb/models.py", line 97, in pre_save
    assert self.shortname == self.json['shortname']
AssertionError

❯ curl -s https://moncoin.faimaison.net/isp.json |jq . 
{
  "subscriberCount": 79,
  "website": "https://www.faimaison.net/",
  "name": "FAImaison",
  "otherWebsites": {
    "Wiki": "https://wiki.faimaison.net/",
    "Gitlab": "https://git.faimaison.net/"
  },
  "memberCount": 109,
  "progressStatus": 7,
  "chatrooms": [
    "irc://irc.geeknode.org/#faimaison"
  ],
  "registeredOffice": {
    "region": "Loire Atlantique",
    "street-address": "7 rue Maurice Sibille",
    "postal-code": "44000",
    "country-name": "France",
    "locality": "Nantes"
  },
  "coordinates": {
    "latitude": 47.2169,
    "longitude": -1.5549
  },
  "mainMailingList": "info@faimaison.net",
  "coveredAreas": [
    {
      "technologies": [
        "wifi"
      ],
      "name": "Accès internet haut débit sans-fil"
    },
    {
      "technologies": [
        "dsl"
      ],
      "name": "ADSL marque blanche FDN"
    },
    {
      "technologies": [
        "dsl"
      ],
      "name": "VPN"
    },
    {
      "technologies": [
        "cube"
      ],
      "name": "Nantes et environs"
    }
  ],
  "version": 0.1,
  "ffdnMemberSince": "2012-06-04",
  "logoURL": "https://www.faimaison.net/theme/images/logo.png",
  "shortname": "FAImaison",
  "creationDate": "2011-01-19",
  "email": "contact@faimaison.net",
  "description": "FAImaison est un fournisseur d'accès à internet offrant un service sur Nantes et ses alentours"
}