internal/dcensus: downgrade stackdriver API errors to log warnings

Change-Id: I0e1e9e8bfb6e0d1bca59a0d598ee3e6efa096c1f
Reviewed-on: https://go-review.googlesource.com/c/pkgsite/+/261820
Trust: Jonathan Amsterdam <jba@google.com>
Run-TryBot: Jonathan Amsterdam <jba@google.com>
Reviewed-by: Julie Qiu <julie@golang.org>
TryBot-Result: kokoro <noreply+kokoro@google.com>
diff --git a/internal/dcensus/dcensus.go b/internal/dcensus/dcensus.go
index 8de6fbd..749c039 100644
--- a/internal/dcensus/dcensus.go
+++ b/internal/dcensus/dcensus.go
@@ -178,7 +178,7 @@
 		MonitoredResource:       mr,
 		DefaultMonitoringLabels: stackdriverLabels(cfg),
 		OnError: func(err error) {
-			log.Errorf(context.Background(), "Stackdriver view exporter: %v", err)
+			log.Warningf(context.Background(), "Stackdriver view exporter: %v", err)
 		},
 	})
 }
diff --git a/internal/dcensus/debug.go b/internal/dcensus/debug.go
index 8bac6f1..fd6134a 100644
--- a/internal/dcensus/debug.go
+++ b/internal/dcensus/debug.go
@@ -35,7 +35,7 @@
 	d.err = nil
 	d.mu.Unlock()
 	if err != nil {
-		log.Errorf(ctx, "trace exporter: %v", err)
+		log.Warningf(ctx, "trace exporter: %v", err)
 		log.Debugf(ctx, "trace exporter SpanData:\n%s", dumpSpanData(s))
 	}
 }