Fix FeatureDeprecatedError being raised without a message

[brendo]

Description

The FeatureDeprecatedError error is currently raised without a message. This makes it near impossible to know what the feature was that was deprecated and leads to a lot of diving through stacktraces to try and figure it out.

This PR goes a little way to making this better by specifying the message when raising the error. This should give developers more clues and speed up investigation.

How has this been tested?

Updated existing unit test.

Checklist:

• My commit message follow the pattern described in here
• I have performed a self-review of my own code.
• I have added tests that prove my fix is effective or that my feature works.
• I have updated the project documentation.
• I have added a changelog line.

[paulomarg]

Thank you!