Python 2 to Python 3 Migration — Partial Work

A colleague has been migrating a legacy web application from Python 2 to Python 3. They got halfway through before being pulled onto another project. You need to prepare a document that will allow a fresh engineer to pick up exactly where things left off.

Here is the current state of the migration work:

What has been done so far

• Identified all 43 Python files in the src/ directory that need changes
• Converted 18 of the 43 files (the auth/ and models/ subdirectories are fully converted)
• Ran the automated 2to3 tool on all converted files; manual review completed for auth/
• Updated requirements.txt — all dependencies now have Python 3 compatible versions pinned
• Confirmed the test suite runs on Python 3.9 for the converted modules (12 of 25 test files pass)

What still needs doing

• Convert remaining 25 files in views/, api/, and utils/
• Complete manual review of converted models/ files (the tool output looks correct but hasn't been human-checked)
• Fix 3 known test failures: test_session.py, test_cache.py, test_legacy_xml.py
• Decide whether to keep the six compatibility shim (currently used in 7 files) or remove it
• Update the CI pipeline configuration (.github/workflows/ci.yml) to switch from Python 2.7 to 3.9

Key files and locations

• Migration tracker spreadsheet: docs/migration_tracker.xlsx
• CI config: .github/workflows/ci.yml
• Main entry point: src/app.py
• Test runner command: pytest src/tests/ -v

Known issues

• utils/xml_parser.py uses a deprecated cElementTree import that 2to3 does not rewrite automatically — the replacement is xml.etree.ElementTree
• The six shim removal is risky in api/compat.py because that file is imported by 14 other modules and has not been audited yet

Produce a handoff document for the engineer who will continue this work.