The migrate_from_trac task fails if a redmine install has required custom fields on a project. To fix this issue, I added a loop that prompts the user to enter values for all the project custom fields, re-prompting if the input value does not validate for the custom field, and providing the default value as expected.

Also, if the project still fails to save for whatever reason, the errors are printed out. Previously, a "method not found on nil::nilClass" was being thrown, which is not as helpful, and was difficult to debug.