Merge pull request #37624 from deads2k/test-01-text

Automatic merge from submit-queue

add wrapper to provide stderr on command errors

The go standard library doesn't include stderr in the error message, but in many cases it is present: https://golang.org/src/os/exec/exec.go#L389 .  This adds a wrapper to display that information. I've added in it on spot where the kops test is having trouble.  If it works well, we can add it elsewhere. 

@wojtek-t ptal

hack/e2e.go

@@ -584,7 +584,7 @@ func clusterSize(deploy deployer) (int, error) {
 	}
 	o, err := exec.Command("kubectl", "get", "nodes", "--no-headers").Output()
 	if err != nil {
-		log.Printf("kubectl get nodes failed: %v", err)
+		log.Printf("kubectl get nodes failed: %s\n%s", WrapError(err).Error(), string(o))
 		return -1, err
 	}
 	stdout := strings.TrimSpace(string(o))
@@ -592,6 +592,35 @@ func clusterSize(deploy deployer) (int, error) {
 	return len(strings.Split(stdout, "\n")), nil
 }
 
+// CommandError will provide stderr output (if available) from structured
+// exit errors
+type CommandError struct {
+	err error
+}
+
+func WrapError(err error) *CommandError {
+	if err == nil {
+		return nil
+	}
+	return &CommandError{err: err}
+}
+
+func (e *CommandError) Error() string {
+	if e == nil {
+		return ""
+	}
+	exitErr, ok := e.err.(*exec.ExitError)
+	if !ok {
+		return e.err.Error()
+	}
+
+	stderr := ""
+	if exitErr.Stderr != nil {
+		stderr = string(stderr)
+	}
+	return fmt.Sprintf("%q: %q", exitErr.Error(), stderr)
+}
+
 func DumpClusterLogs(location string) error {
 	log.Printf("Dumping cluster logs to: %v", location)
 	return finishRunning("dump cluster logs", exec.Command("./cluster/log-dump.sh", location))