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• Lowering down pylint warnings (260 -> 180, only "line too long" or "statement too complex" left).
• Multiple typos.
• Using (multi line) formatted string literals instead of .format().
• Extracted subprocess opening calls to a separate function.
• Extracted stack traces printing function.
• Extracted test skipping functions (bonus: -1 nest level).
• Extracted test suites and tests inside a suite sorting key functions.
• Setting ClickHouse default TCP port in main function.
• Added spaces where necessary.