The reproduction steps described in bug 3328 could not be reproduced.

When following the steps, I would receive a HTTP 500 error when

making the second post. This is a result of Django not being used

previously to validate the data. Instead it was being left to the

database, which is checked and handled differently depending on

which database is used and it's configuration. To fix this creation

was changed to instantiation to prevent partial saving, a validation

step was added prior to saving, a new webapi error was added, and

the error code was documented in the manual.

I tested to ensure when making the second rbt post that the error was

caught and an informative error message was displayed, rather than an

HTTP 500 error. I also checked after the failure to ensure that a

partial review object was not created. I also tested to ensure that

posts could still be created if they had a unique commit id.