Avoid back and forth conversion between strings and bytes.

Signed-off-by: Anusha Ragunathan <anusha@docker.com>
(cherry picked from commit d6d448aab8)

cli/error.go

@@ -1,21 +1,20 @@
 package cli
 
-import "bytes"
+import "strings"
 
 // Errors is a list of errors.
 // Useful in a loop if you don't want to return the error right away and you want to display after the loop,
 // all the errors that happened during the loop.
 type Errors []error
 
-func (errs Errors) Error() string {
-	if len(errs) < 1 {
+func (errList Errors) Error() string {
+	if len(errList) < 1 {
 		return ""
 	}
-	var buf bytes.Buffer
-	buf.WriteString(errs[0].Error())
-	for _, err := range errs[1:] {
-		buf.WriteString(", ")
-		buf.WriteString(err.Error())
+
+	out := make([]string, len(errList))
+	for i := range errList {
+		out[i] = errList[i].Error()
 	}
-	return buf.String()
+	return strings.Join(out, ", ")
 }