Fixed regression in text formatter

Author: cmaglie

common/formatter/print_test.go

@@ -62,11 +62,14 @@ func ExamplePrint() {
 func ExamplePrint_alternative() {
 	formatter.SetFormatter("text")
 	formatter.Print(TestStruct{5})
+	formatter.Print("a string")
 
 	formatter.SetFormatter("json")
 	formatter.Print(TestStruct{10})
+	formatter.Print("a string")
 
 	// Output:
 	// VALUE = 5
+	// a string
 	// {"value":10}
 }

common/formatter/text.go

@@ -34,6 +34,9 @@ func (tp *TextFormatter) Format(msg interface{}) (string, error) {
 	if msg == nil {
 		return "<nil>", nil
 	}
+	if str, ok := msg.(string); ok {
+		return str, nil
+	}
 	str, ok := msg.(fmt.Stringer)
 	if !ok {
 		return "", errors.New("object can't be formatted as text")