django - Integrity error when Google users try to connect (old users) -

we have django-social-auth used enable google sign-ins in our app. people created google account can connect while older can’t – integrityerror.

i have no idea how google oauth works on google side, don’t why change users others. have 3 backends activated (googleoauth, googleoauth2, googleopenid). , can’t find documentation integrityerror. we’re using django.

any idea?

edit: error requested

pgpool: 2016-04-07 10:33:13 log: pid 27330: pool_send_and_wait: error or notice message backend: : db node id: 0 backend pid: 3539 statement: insert "auth_user" ("password", "last_login", "is_superuser", "username", "first_name", "last_name", "email", "is_staff", "is_active", "date_joined") values ('!', '2016-04-07 08:33:13.123859+00:00', false, '**************', '', '', '****************@gmail.com', false, true, '2016-04-07 08:33:13.123859+00:00') returning "auth_user"."id" message: la valeur d'une clé dupliquée rompt la contrainte unique « auth_user_email_key »