This is hiding a real bundler issue as a "network error". It's more
helpful to get a proper bug report, with stack trace and so on.
So stop re-raising errors when evaluating unmarshaled responses as
network errors, and only raise Marshal errors when the Marshal format is
invalid, not whenever marshalled gemspecs can't be loaded because that
may hide actual client errors, like missing `YAML` constants.
https://github.com/rubygems/rubygems/commit/05ea907e1c
d32fa986c3