Recent versions of excon have a middleware component,
Excon::Middleware::Expects and fog requests mostly record an expectation
of a 200 status code. Some calls to AWS return status other than 200 and
in some cases the error handling obscures the underlying error.
Current handling parsed error.message; this instance of error is
constructed by excon and includes the response as an attribute. The
message is always something like 'Expected(200) <=> Actual(404 Not Found)'
and so the parsing never succeeds.
Instead we now attempt to parse error.response.body which should allow
extraction of the underlying AWS Code value, which in turn will produce
an exception that points to the actual underlying cause.
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