- In D20986, the "LintRenderer" classes swapped to a modern modular pattern.
- This invokes all of their constructors as a side effect.
- The ArcanistCheckstyleXMLLintRenderer linter is written in an un-modern way and causes significant side effects during construction, notably failing if the XML extension which provides XMLWriter is not installed.
- ArcanistCheckstyleXMLLintRenderer should not instantiate XMLWriter on construction.
- If the xml extension is not available, ArcanistCheckstyleXMLLintRenderer should fail more clearly/gracefully.