src/pkg/[n-z]*: gofix -r error -force=error

R=golang-dev, bsiegert, iant
CC=golang-dev
https://golang.org/cl/5294074
diff --git a/src/pkg/old/netchan/netchan_test.go b/src/pkg/old/netchan/netchan_test.go
index 8c0f9a6..d11a670 100644
--- a/src/pkg/old/netchan/netchan_test.go
+++ b/src/pkg/old/netchan/netchan_test.go
@@ -156,7 +156,7 @@
 	}()
 	select {
 	case err = <-imp.Errors():
-		if strings.Index(err.String(), "no such channel") < 0 {
+		if strings.Index(err.Error(), "no such channel") < 0 {
 			t.Error("wrong error for nonexistent channel:", err)
 		}
 	case <-timeout: