ENG-16116 - ValidationError when group name already exists

- source :: https://15five-dev.atlassian.net/browse/ENG-16116

- tags :: Jira 15Five Bugs Partnership Squad Sentry

Description

The real problem here is that we're raising a ValidationError for a form but then the same function gets used outside the view and throws the exception to Sentry rather than surfacing it to the user.