Use service catalog to get services URLs
diff --git a/openstack/endpoint_location.go b/openstack/endpoint_location.go
index 5a311e4..29d02c4 100644
--- a/openstack/endpoint_location.go
+++ b/openstack/endpoint_location.go
@@ -5,9 +5,7 @@
 
 	"github.com/rackspace/gophercloud"
 	tokens2 "github.com/rackspace/gophercloud/openstack/identity/v2/tokens"
-	endpoints3 "github.com/rackspace/gophercloud/openstack/identity/v3/endpoints"
-	services3 "github.com/rackspace/gophercloud/openstack/identity/v3/services"
-	"github.com/rackspace/gophercloud/pagination"
+	tokens3 "github.com/rackspace/gophercloud/openstack/identity/v3/tokens"
 )
 
 // V2EndpointURL discovers the endpoint URL for a specific service from a ServiceCatalog acquired
@@ -52,73 +50,42 @@
 	return "", gophercloud.ErrEndpointNotFound
 }
 
-// V3EndpointURL discovers the endpoint URL for a specific service using multiple calls against
-// an identity v3 service endpoint. The specified EndpointOpts are used to identify a unique,
+// V3EndpointURL discovers the endpoint URL for a specific service from a Catalog acquired
+// during the v3 identity service. The specified EndpointOpts are used to identify a unique,
 // unambiguous endpoint to return. It's an error both when multiple endpoints match the provided
 // criteria and when none do. The minimum that can be specified is a Type, but you will also often
 // need to specify a Name and/or a Region depending on what's available on your OpenStack
 // deployment.
-func V3EndpointURL(v3Client *gophercloud.ServiceClient, opts gophercloud.EndpointOpts) (string, error) {
-	// Discover the service we're interested in.
-	var services = make([]services3.Service, 0, 1)
-	servicePager := services3.List(v3Client, services3.ListOpts{ServiceType: opts.Type})
-	err := servicePager.EachPage(func(page pagination.Page) (bool, error) {
-		part, err := services3.ExtractServices(page)
-		if err != nil {
-			return false, err
-		}
-
-		for _, service := range part {
-			if service.Name == opts.Name {
-				services = append(services, service)
+func V3EndpointURL(catalog *tokens3.ServiceCatalog, opts gophercloud.EndpointOpts) (string, error) {
+	// Extract Endpoints from the catalog entries that match the requested Type, Interface,
+	// Name if provided, and Region if provided.
+	var endpoints = make([]tokens3.Endpoint, 0, 1)
+	for _, entry := range catalog.Entries {
+		if (entry.Type == opts.Type) && (opts.Name == "" || entry.Name == opts.Name) {
+			for _, endpoint := range entry.Endpoints {
+				if opts.Availability != gophercloud.AvailabilityAdmin &&
+					opts.Availability != gophercloud.AvailabilityPublic &&
+					opts.Availability != gophercloud.AvailabilityInternal {
+					return "", fmt.Errorf("Unexpected availability in endpoint query: %s", opts.Availability)
+				}
+				if (opts.Availability == gophercloud.Availability(endpoint.Interface)) &&
+					(opts.Region == "" || endpoint.Region == opts.Region) {
+					endpoints = append(endpoints, endpoint)
+				}
 			}
 		}
-
-		return true, nil
-	})
-	if err != nil {
-		return "", err
 	}
 
-	if len(services) == 0 {
-		return "", gophercloud.ErrServiceNotFound
-	}
-	if len(services) > 1 {
-		return "", fmt.Errorf("Discovered %d matching services: %#v", len(services), services)
-	}
-	service := services[0]
-
-	// Enumerate the endpoints available for this service.
-	var endpoints []endpoints3.Endpoint
-	endpointPager := endpoints3.List(v3Client, endpoints3.ListOpts{
-		Availability: opts.Availability,
-		ServiceID:    service.ID,
-	})
-	err = endpointPager.EachPage(func(page pagination.Page) (bool, error) {
-		part, err := endpoints3.ExtractEndpoints(page)
-		if err != nil {
-			return false, err
-		}
-
-		for _, endpoint := range part {
-			if opts.Region == "" || endpoint.Region == opts.Region {
-				endpoints = append(endpoints, endpoint)
-			}
-		}
-
-		return true, nil
-	})
-	if err != nil {
-		return "", err
-	}
-
-	if len(endpoints) == 0 {
-		return "", gophercloud.ErrEndpointNotFound
-	}
+	// Report an error if the options were ambiguous.
 	if len(endpoints) > 1 {
 		return "", fmt.Errorf("Discovered %d matching endpoints: %#v", len(endpoints), endpoints)
 	}
-	endpoint := endpoints[0]
 
-	return gophercloud.NormalizeURL(endpoint.URL), nil
+	// Extract the URL from the matching Endpoint.
+	for _, endpoint := range endpoints {
+		return gophercloud.NormalizeURL(endpoint.URL), nil
+	}
+
+	// Report an error if there were no matching endpoints.
+	return "", gophercloud.ErrEndpointNotFound
 }