Add migration warning and option to migrate to labels.

Signed-off-by: Daniel Nephin <dnephin@gmail.com>

compose/project.py

@@ -1,13 +1,14 @@
 from __future__ import unicode_literals
 from __future__ import absolute_import
 import logging
-
 from functools import reduce
+
+from docker.errors import APIError
+
 from .config import get_service_name_from_net, ConfigurationError
 from .const import LABEL_PROJECT, LABEL_ONE_OFF
-from .service import Service
+from .service import Service, check_for_legacy_containers
 from .container import Container
-from docker.errors import APIError
 
 log = logging.getLogger(__name__)
 
@@ -82,6 +83,10 @@ class Project(object):
                                             volumes_from=volumes_from, **service_dict))
         return project
 
+    @property
+    def service_names(self):
+        return [service.name for service in self.services]
+
     def get_service(self, name):
         """
         Retrieve a service by name. Raises NoSuchService
@@ -109,7 +114,7 @@ class Project(object):
         """
         if service_names is None or len(service_names) == 0:
             return self.get_services(
-                service_names=[s.name for s in self.services],
+                service_names=self.service_names,
                 include_deps=include_deps
             )
         else:
@@ -230,10 +235,21 @@ class Project(object):
             service.remove_stopped(**options)
 
     def containers(self, service_names=None, stopped=False, one_off=False):
-        return [Container.from_ps(self.client, container)
-                for container in self.client.containers(
-                    all=stopped,
-                    filters={'label': self.labels(one_off=one_off)})]
+        containers = [
+            Container.from_ps(self.client, container)
+            for container in self.client.containers(
+                all=stopped,
+                filters={'label': self.labels(one_off=one_off)})]
+
+        if not containers:
+            check_for_legacy_containers(
+                self.client,
+                self.name,
+                self.service_names,
+                stopped=stopped,
+                one_off=one_off)
+
+        return containers
 
     def _inject_deps(self, acc, service):
         net_name = service.get_net_name()