Improve utils.FatalError error formatting (#34417)

* Use existing error formatting logic from `trace`

* Remove unnecessary layer of indirection

* Add test for UserMessageFromError

* Fix imports

lib/utils/cli.go

@@ -178,21 +178,15 @@ func UserMessageFromError(err error) string {
 // The error message is escaped if necessary. A newline is added if the error text
 // does not end with a newline.
 func FormatErrorWithNewline(err error) string {
-	message := formatError(err)
+	var buf bytes.Buffer
+	formatErrorWriter(err, &buf)
+	message := buf.String()
 	if !strings.HasSuffix(message, "\n") {
 		message = message + "\n"
 	}
 	return message
 }
 
-// formatError returns user friendly error message from error.
-// The error message is escaped if necessary
-func formatError(err error) string {
-	var buf bytes.Buffer
-	formatErrorWriter(err, &buf)
-	return buf.String()
-}
-
 // formatErrorWriter formats the specified error into the provided writer.
 // The error message is escaped if necessary
 func formatErrorWriter(err error, w io.Writer) {
@@ -203,22 +197,15 @@ func formatErrorWriter(err error, w io.Writer) {
 		fmt.Fprintln(w, certErr)
 		return
 	}
-	// If the error is a trace error, check if it has a user message embedded in
-	// it, if it does, print it, otherwise escape and print the original error.
-	if traceErr, ok := err.(*trace.TraceErr); ok {
-		for _, message := range traceErr.Messages {
-			fmt.Fprintln(w, AllowWhitespace(message))
-		}
-		fmt.Fprintln(w, AllowWhitespace(trace.Unwrap(traceErr).Error()))
+
+	msg := trace.UserMessage(err)
+	// Error can be of type trace.proxyError where error message didn't get captured.
+	if msg == "" {
+		fmt.Fprintln(w, "please check Teleport's log for more details")
 		return
 	}
-	strErr := err.Error()
-	// Error can be of type trace.proxyError where error message didn't get captured.
-	if strErr == "" {
-		fmt.Fprintln(w, "please check Teleport's log for more details")
-	} else {
-		fmt.Fprintln(w, AllowWhitespace(err.Error()))
-	}
+
+	fmt.Fprintln(w, AllowWhitespace(msg))
 }
 
 func formatCertError(err error) string {

lib/utils/cli_test.go

@@ -19,17 +19,21 @@ package utils
 import (
 	"crypto/x509"
 	"fmt"
-	"strings"
 	"testing"
 
 	"github.com/gravitational/trace"
+	"github.com/sirupsen/logrus"
 	"github.com/stretchr/testify/require"
 )
 
 func TestUserMessageFromError(t *testing.T) {
-	t.Parallel()
+	// Behavior is different in debug
+	priorLevel := logrus.GetLevel()
+	logrus.SetLevel(logrus.InfoLevel)
+	t.Cleanup(func() {
+		logrus.SetLevel(priorLevel)
+	})
 
-	t.Skip("Enable after https://drone.gravitational.io/gravitational/teleport/3517 is merged.")
 	tests := []struct {
 		comment   string
 		inError   error
@@ -47,14 +51,14 @@ func TestUserMessageFromError(t *testing.T) {
 		},
 		{
 			comment:   "outputs user message as provided",
-			inError:   trace.Errorf("\x1b[1mWARNING\x1b[0m"),
-			outString: `error: "\x1b[1mWARNING\x1b[0m"`,
+			inError:   trace.Errorf("bad thing occurred"),
+			outString: "\x1b[31mERROR: \x1b[0mbad thing occurred",
 		},
 	}
 
 	for _, tt := range tests {
 		message := UserMessageFromError(tt.inError)
-		require.True(t, strings.HasPrefix(message, tt.outString), tt.comment)
+		require.Contains(t, message, tt.outString)
 	}
 }