So a duplicate fingerprint would fail to pass unique test. Fixes:

+ francedata_import_representatives
cTraceback (most recent call last):
  File "/home/jpic/work/lqdn/lqdn_env/bin/francedata_import_representatives", line 9, in <module>
    load_entry_point('django-representatives==0.0.19', 'console_scripts', 'francedata_import_representatives')()
  File "/home/jpic/work/lqdn/django-representatives/representatives/contrib/francedata/import_representatives.py", line 317, in main
    an_importer.manage_rep(rep)
  File "/home/jpic/work/lqdn/lqdn_env/lib/python2.7/site-packages/django/utils/decorators.py", line 145, in inner
    return func(*args, **kwargs)
  File "/home/jpic/work/lqdn/django-representatives/representatives/contrib/francedata/import_representatives.py", line 145, in manage_rep
    self.add_mandates(representative, rep_json)
  File "/home/jpic/work/lqdn/django-representatives/representatives/contrib/francedata/import_representatives.py", line 184, in add_mandates
    name=rep_json.get('parti_ratt_financier'), country=self.france)
  File "/home/jpic/work/lqdn/lqdn_env/lib/python2.7/site-packages/django/db/models/manager.py", line 127, in manager_method
    return getattr(self.get_queryset(), name)(*args, **kwargs)
  File "/home/jpic/work/lqdn/lqdn_env/lib/python2.7/site-packages/django/db/models/query.py", line 407, in get_or_create
    return self._create_object_from_params(lookup, params)
  File "/home/jpic/work/lqdn/lqdn_env/lib/python2.7/site-packages/django/db/models/query.py", line 447, in _create_object_from_params
    six.reraise(*exc_info)
  File "/home/jpic/work/lqdn/lqdn_env/lib/python2.7/site-packages/django/db/models/query.py", line 439, in _create_object_from_params
    obj = self.create(**params)
  File "/home/jpic/work/lqdn/lqdn_env/lib/python2.7/site-packages/django/db/models/query.py", line 348, in create
    obj.save(force_insert=True, using=self.db)
  File "/home/jpic/work/lqdn/django-representatives/representatives/models.py", line 68, in save
    super(HashableModel, self).save(*args, **kwargs)
  File "/home/jpic/work/lqdn/lqdn_env/lib/python2.7/site-packages/django/db/models/base.py", line 734, in save
    force_update=force_update, update_fields=update_fields)
  File "/home/jpic/work/lqdn/lqdn_env/lib/python2.7/site-packages/django/db/models/base.py", line 762, in save_base
    updated = self._save_table(raw, cls, force_insert, force_update, using, update_fields)
  File "/home/jpic/work/lqdn/lqdn_env/lib/python2.7/site-packages/django/db/models/base.py", line 846, in _save_table
    result = self._do_insert(cls._base_manager, using, fields, update_pk, raw)
  File "/home/jpic/work/lqdn/lqdn_env/lib/python2.7/site-packages/django/db/models/base.py", line 885, in _do_insert
    using=using, raw=raw)
  File "/home/jpic/work/lqdn/lqdn_env/lib/python2.7/site-packages/django/db/models/manager.py", line 127, in manager_method
    return getattr(self.get_queryset(), name)(*args, **kwargs)
  File "/home/jpic/work/lqdn/lqdn_env/lib/python2.7/site-packages/django/db/models/query.py", line 920, in _insert
    return query.get_compiler(using=using).execute_sql(return_id)
  File "/home/jpic/work/lqdn/lqdn_env/lib/python2.7/site-packages/django/db/models/sql/compiler.py", line 974, in execute_sql
    cursor.execute(sql, params)
  File "/home/jpic/work/lqdn/lqdn_env/lib/python2.7/site-packages/django/db/backends/utils.py", line 64, in execute
    return self.cursor.execute(sql, params)
  File "/home/jpic/work/lqdn/lqdn_env/lib/python2.7/site-packages/django/db/utils.py", line 98, in __exit__
    six.reraise(dj_exc_type, dj_exc_value, traceback)
  File "/home/jpic/work/lqdn/lqdn_env/lib/python2.7/site-packages/django/db/backends/utils.py", line 64, in execute
    return self.cursor.execute(sql, params)
  File "/home/jpic/work/lqdn/lqdn_env/lib/python2.7/site-packages/django/db/backends/sqlite3/base.py", line 318, in execute
    return Database.Cursor.execute(self, query, params)
django.db.utils.IntegrityError: UNIQUE constraint failed: representatives_constituency.fingerprint