[IMPROVEMENT] Changed the error message when adding an infraction

[janssensjelle]

Types of changes

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• Bugfix (non-breaking change which fixes an issue).
• New feature (non-breaking change which adds functionality).
• Breaking change (fix or feature that would cause existing functionality not to work as expected).
• Documentation Update (if none of the other choices applies).

Proposed changes

When adding an infraction and Hackster cannot dm the user due to permissions, it will send an error message:
"Could not DM member due to privacy settings, however will still attempt to ban them..."

The user is not being banned. This can cause confusion. Also added some testing for it.

Checklist

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• I have read and followed the CONTRIBUTING.md
  doc.
• Lint and unit tests pass locally with my changes.
• I have added the necessary documentation (if appropriate).

Additional context

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