Utility rank_zero_only doesn't properly handle environment variable LOCAL_RANK
🐛 Bug
The LOCAL_RANK environment variable can be a string. This causes checks in the rank_zero_only decorator to fail here: https://github.com/PyTorchLightning/pytorch-lightning/blob/master/pytorch_lightning/utilities/distributed.py#L11
Expected behavior
We should cast LOCAL_RANK to an int both in the rank_zero_only check as well as in the trainer here: https://github.com/PyTorchLightning/pytorch-lightning/blob/master/pytorch_lightning/trainer/trainer.py#L385
Then the decorator works as we expected