Allow a combination of labels for tag discover

Some downstream build pipelines do not apply a label which exactly
matches the version tag. The only way to build the full versioned tag
is by combining multiple labels in a template pattern.

This change uses a python string.format syntax to allow multiple tags
to be combined.

Change-Id: Id0fb010ebcdd4d3f3650c94065fc42489475c42c
Closes-Bug: #1743883

tripleo_common/image/image_uploader.py

@@ -273,12 +273,23 @@ class DockerImageUploader(ImageUploader):
                 'No label specified. Available labels: %s' % label_keys
             )
 
-        tag_label = labels.get(tag_from_label)
-        if tag_label is None:
-            raise ImageUploaderException(
-                'Image %s has no label %s. Available labels: %s' %
-                (image, tag_from_label, label_keys)
-            )
+        if "{" in tag_from_label:
+            try:
+                tag_label = tag_from_label.format(**labels)
+            except ValueError as e:
+                raise ImageUploaderException(e)
+            except KeyError as e:
+                raise ImageUploaderException(
+                    'Image %s %s. Available labels: %s' %
+                    (image, e, label_keys)
+                )
+        else:
+            tag_label = labels.get(tag_from_label)
+            if tag_label is None:
+                raise ImageUploaderException(
+                    'Image %s has no label %s. Available labels: %s' %
+                    (image, tag_from_label, label_keys)
+                )
 
         # confirm the tag exists by checking for an entry in RepoTags
         repo_tags = i.get('RepoTags', [])

tripleo_common/tests/image/test_image_uploader.py

@@ -291,9 +291,11 @@ class TestDockerImageUploader(base.TestCase):
         result = {
             'Labels': {
                 'rdo_version': 'a',
-                'build_version': '4.0.0'
+                'build_version': '4.0.0',
+                'release': '1.0.0',
+                'version': '20180125'
             },
-            'RepoTags': ['a']
+            'RepoTags': ['a', '1.0.0-20180125']
         }
         mock_process = mock.Mock()
         mock_process.communicate.return_value = (json.dumps(result), '')
@@ -301,12 +303,34 @@ class TestDockerImageUploader(base.TestCase):
         mock_popen.return_value = mock_process
 
         sr = image_uploader.SECURE_REGISTRIES
+        # simple label -> tag
         self.assertEqual(
             ('docker.io/t/foo', 'a'),
             image_uploader.discover_tag_from_inspect(
                 ('docker.io/t/foo', 'rdo_version', sr))
         )
 
+        # templated labels -> tag
+        self.assertEqual(
+            ('docker.io/t/foo', '1.0.0-20180125'),
+            image_uploader.discover_tag_from_inspect(
+                ('docker.io/t/foo', '{release}-{version}', sr))
+        )
+
+        # Invalid template
+        self.assertRaises(
+            ImageUploaderException,
+            image_uploader.discover_tag_from_inspect,
+            ('docker.io/t/foo', '{release}-{version', sr)
+        )
+
+        # Missing label in template
+        self.assertRaises(
+            ImageUploaderException,
+            image_uploader.discover_tag_from_inspect,
+            ('docker.io/t/foo', '{releases}-{version}', sr)
+        )
+
         # no tag_from_label specified
         self.assertRaises(
             ImageUploaderException,