Summary:
The goal is to return an error code > 127 in the case of a
transient, retryable, infrastructure error. This diff generates
those in the case of failure in downloading a URL or from interacting
with LFS.
Reviewed By: strager
Differential Revision: D15266838
fbshipit-source-id: 4f52a791320123968869032c37912dded464a86e
