一度招待した追加講演者を再度登録しようとするとエラーに成る

[miurahr]

IntegrityError at /2015/proposals/1/speakers/
duplicate key value violates unique constraint "symposion_speakers_speaker_invite_email_key"
DETAIL:  Key (invite_email)=(miurahr@gmail.com) already exists.
Request Method: POST
Request URL:    http://staging.stateofthemap.jp/2015/proposals/1/speakers/
Django Version: 1.7.8
Exception Type: IntegrityError
Exception Value:    
duplicate key value violates unique constraint "symposion_speakers_speaker_invite_email_key"
DETAIL:  Key (invite_email)=(miurahr@gmail.com) already exists.
Exception Location: /srv/sites/sotmjp-website/env/sotmjp-website/local/lib/python2.7/site-packages/django/db/backends/utils.py in execute, line 65
Python Executable:  /srv/sites/sotmjp-website/env/sotmjp-website/bin/python
Python Version: 2.7.6
Python Path:    
['/srv/sites/sotmjp-website',
 '/srv/sites/sotmjp-website/env/sotmjp-website/bin',
 '/srv/sites/sotmjp-website/env/sotmjp-website/src/django-mailer',
 '/srv/sites/sotmjp-website/env/sotmjp-website/src/python-rtfng',
 '/srv/sites/sotmjp-website/env/sotmjp-website/src/restcms',
 '/srv/sites/sotmjp-website/env/sotmjp-website/src/django-admin-tabs',
 '/srv/sites/sotmjp-website/env/sotmjp-website/src/django-admin-tools',
 '/srv/sites/sotmjp-website/env/sotmjp-website/src/symposion',
 '/srv/sites/sotmjp-website/env/sotmjp-website/lib/python2.7',
 '/srv/sites/sotmjp-website/env/sotmjp-website/lib/python2.7/plat-x86_64-linux-gnu',
 '/srv/sites/sotmjp-website/env/sotmjp-website/lib/python2.7/lib-tk',
 '/srv/sites/sotmjp-website/env/sotmjp-website/lib/python2.7/lib-old',
 '/srv/sites/sotmjp-website/env/sotmjp-website/lib/python2.7/lib-dynload',
 '/usr/lib/python2.7',
 '/usr/lib/python2.7/plat-x86_64-linux-gnu',
 '/usr/lib/python2.7/lib-tk',
 '/srv/sites/sotmjp-website/env/sotmjp-website/local/lib/python2.7/site-packages']
Server time:    土, 25 7月 2015 16:50:57 +0900

[miurahr]

formの動作のレアケースでDB内部の異常が発生したためと、判断する。