GetNamespaceLabelsSnapshot has a fallback when it gets errors when looking up a
namespace, therefore reporting the error is more informational than a real
error. In particular, not finding the namespace is normal when running
test/integration/scheduler_perf and happens so frequently that there is a lot
of output on stderr:
E0120 12:19:09.204768 95305 plugin.go:138] "getting namespace, assuming empty set of namespace labels" err="namespace \"namespace-1\" not found" namespace="namespace-1"
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