Log Message:
py-isort: updated to 4.3.12

4.3.12:
- Fix error caused when virtual environment not detected

4.3.11:
- Fixed issue: confused by symlinks pointing to virtualenv gives FIRSTPARTY not \ 
THIRDPARTY
- Fixed issue: current version skips every file on travis
- Additional caching to reduce performance regression introduced in 4.3.5
- Improved handling of pex files and other binary Python files