Rails5 fix NoMethodError: undefined method 'message' for nil:NilClass

What does this MR do?

Fix Rails5 specs to wrap the exceptions for Rails 5 instead of passing it to the initialiser. Rails commit: https://github.com/rails/rails/commit/266455cf25aba942b8717ceb0269d66f719b5696

Are there points in the code the reviewer needs to double check?

Is there a better way to mock wrapped exceptions? 🤷

Why was this MR needed?

rails5 upgrade

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Conform by the code review guidelines
  • Has been reviewed by a Backend maintainer
  • Has been reviewed by a Database specialist
• EE specific content should be in the top level /ee folder
• Conform by the merge request performance guides
• Conform by the style guides
• Conform by the database guides
• If you have multiple commits, please combine them into a few logically organized commits by squashing them
• End-to-end tests pass (package-and-qa manual pipeline job)

What are the relevant issue numbers?

Closes #6605 (closed)