ioPath - fix Flake8 error
ioPath - fix Flake8 error

Summary:
`async_torch_test.py` was failing Flake8 due to a timeout caused by this line:
```
large = "*"*1000000000
```

Not sure what Flake8 does here... but when I removed this line, Flake8 finished almost immediately. This diff changes the syntax to satisfy Flake8.

Also not sure why it didn't raise an error when I initially pushed this code...

Reviewed By: sujitoc

Differential Revision: D27276581

fbshipit-source-id: 9e302b18f46aa56e4346e44f0484f3df3e83779e

facebookresearch/iopath,facebookresearch/iopath