Fix "Prefer `format()` over string interpolation operator" issue

[tomato42]

This pull request automatically fixes all occurrences of the following issue:

Issue type: Prefer format() over string interpolation operator Issue details: https://www.quantifiedcode.com/app/project/gh:tomato42:tlslite-ng?groups=code_patterns/%3A4ACGxFj1

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Cheers, Cody - Your code quality bot

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