Fix: avoid race condition on model zoo directory creation (#16578)
Summary:
The current implementation of the `torch.utils.model_zoo.load_url`
function is prone to a race condition when creating the directory in
which it saves the loaded models, since it checks whether the
directory exists and then creates it in two separate steps. The
directory can be created after the check was made but before we
attempt to create the directory, resulting in an unhandled exception.
Instead, try to create the directory directly, and do nothing if it
already exists.
Note: for Python versions ≥ 3.2, we could simply use the
`exist_ok=True` flag on `os.makedirs`, but this is unavailable in
Python 2.7.
Signed-off-by: Antoine Busque <antoine.busque@elementai.com>
Pull Request resolved: https://github.com/pytorch/pytorch/pull/16578
Differential Revision: D13886470
Pulled By: soumith
fbshipit-source-id: 88815c8a65eec96caea32d6e9a7f83802502fdb9
