Unify error messages

inlineXHTMLContent.go

@@ -2,7 +2,6 @@ package atom
 
 import (
 	"encoding/xml"
-	"errors"
 	"fmt"
 )
 
@@ -43,11 +42,11 @@ func (i *InlineXHTMLContent) getType() string { return i.Type }
 // returns an error.
 func (i *InlineXHTMLContent) Check() error {
 	if i.Type != "xhtml" {
-		return errors.New("type attribute of inline xhtml content must be xhtml")
+		return fmt.Errorf("type attribute of inline xhtml content %v must be xhtml", i)
 	}
 
 	if err := i.XHTMLDiv.Check(); err != nil {
-		return fmt.Errorf("xhtml div element %v of inline xhtml content %v: %v", i.XHTMLDiv, i, err)
+		return fmt.Errorf("xhtml div element of inline xhtml content %v: %v", i, err)
 	}
 
 	return nil