Abstracting url paths a bit better
diff --git a/openstack/identity/v2/extensions/admin/roles/urls.go b/openstack/identity/v2/extensions/admin/roles/urls.go
index 9400782..170658d 100644
--- a/openstack/identity/v2/extensions/admin/roles/urls.go
+++ b/openstack/identity/v2/extensions/admin/roles/urls.go
@@ -2,16 +2,19 @@
 
 import "github.com/rackspace/gophercloud"
 
-const extPath = "OS-KSADMN/roles"
+const (
+	ExtPath  = "OS-KSADMN/roles"
+	UserPath = "users"
+)
 
 func resourceURL(c *gophercloud.ServiceClient, id string) string {
-	return c.ServiceURL(extPath, id)
+	return c.ServiceURL(ExtPath, id)
 }
 
 func rootURL(c *gophercloud.ServiceClient) string {
-	return c.ServiceURL(extPath)
+	return c.ServiceURL(ExtPath)
 }
 
 func userRoleURL(c *gophercloud.ServiceClient, tenantID, userID, roleID string) string {
-	return c.ServiceURL("tenants", tenantID, "users", userID, extPath, roleID)
+	return c.ServiceURL("tenants", tenantID, UserPath, userID, ExtPath, roleID)
 }