Add file path to errors loading the key file

Signed-off-by: Derek McGowan <derek@mcgstyle.net> (github: dmcgowan)

api/common.go

@@ -69,7 +69,7 @@ func LoadOrCreateTrustKey(trustKeyPath string) (libtrust.PrivateKey, error) {
 			return nil, fmt.Errorf("Error saving key file: %s", err)
 		}
 	} else if err != nil {
-		return nil, fmt.Errorf("Error loading key file: %s", err)
+		return nil, fmt.Errorf("Error loading key file %s: %s", trustKeyPath, err)
 	}
 	return trustKey, nil
 }