Changed directory structure.

google/internal/externalaccount/err.go

@@ -0,0 +1,14 @@
+package externalaccount
+
+import "fmt"
+
+//Error for handling OAuth related error responses as stated in rfc6749#5.2.
+type Error struct {
+	Code        string
+	URI         string
+	Description string
+}
+
+func (err *Error) Error() string {
+	return fmt.Sprintf("got error code %s from %s: %s", err.Code, err.URI, err.Description)
+}