[SDKs] Improve wording of Keep error messages in Python SDK
This is what we have:
arvados.errors.KeepReadError: failed to read 33b13624f658eef3a4e5da5bcae81487+67108864+A8d000f7060ec43f0247372fbfdf2174f810dcacd@599abf34: service http://keep1.4xphq.arvadosapi.com:25107/ responded with 0 (6, 'Could not resolve host: keep1.4xphq.arvadosapi.com'); service http://keep0.4xphq.arvadosapi.com:25107/ responded with 0 (6, 'Could not resolve host: keep0.4xphq.arvadosapi.com')
The "service responded with" language makes it sound like keep1 and keep0 are having DNS problems, but in fact it's the local machine (a compute node in this case) having DNS problems.
Suggestion: "http://keep1.4xphq.arvadosapi.com:25107/ status was 0 (6, ...)"