Retry/skip test on URLError rather than on HTTPError (#39477)
Summary:
`HTTPError` are raised when server is overloaded, while `URLError` is
raised when network is not available
And since `HTTPError` is an extension of `URLError`, `URLError` should catch both exceptions
Pull Request resolved: https://github.com/pytorch/pytorch/pull/39477
Differential Revision: D21873560
Pulled By: malfet
fbshipit-source-id: 11806671b768705465f562087521ad4887fd20f7
