Goal

Implement a hacking check to prevent eventlet from being accidentally reintroduced into the Heat codebase after its migration away from eventlet. This follows the post-migration guidance from the eventlet removal project which recommends adding specific checks using the OpenStack Hacking framework to block eventlet imports at code review time.

Goal statement

Add a new hacking check (HE305) that automatically detects and prevents any attempt to import eventlet or its submodules, ensuring Heat maintains its eventlet-free status and preventing potential security and maintenance issues associated with eventlet.

Acceptance Criteria

• Verify that a new hacking check HE305 is implemented in heat/hacking/checks.py
• Verify that the check detects direct eventlet imports (import eventlet)
• Verify that the check detects from eventlet imports (from eventlet import ...)
• Verify that the check is registered in tox.ini flake8 local-plugins configuration
• Verify that comprehensive unit tests are added to heat/tests/test_hacking.py covering both positive and negative test cases
• Verify that HACKING.rst documentation is updated to include the new HE305 rule
• Verify that the check fails when eventlet import is detected and passes when no eventlet import is present
• Verify that the check ignores commented eventlet imports
• Verify that the check works with various whitespace patterns and indentation levels