* add ddp script variations
* add ddp test
* rename
* shell
* test
* test
* try call
* try without subprocess
* test
* display the error
* list all variations
* try string
* try copy env
* debug
* pythonpath
* path
* update test
* change
* simple ddp test
* replace
* remove random port
* random port
* str
* clean up
* check run spawn
* clean up
* docs
* docs
* update test
* docs
* changelog
* changelog
* Fix local rank zero casting
The environment variable 'LOCAL_RANK' can be a string, causing the `if rank_zero_only.rank == 0` check to fail
* Update distributed.py
address comment