tracker: Add extra check to verify tracker-extract has run

Summary:
"?urn nie:dataSource tracker:extractor-data-source" is a
property added by tracker-extract when it adds all metadata.

Reviewers: smcv, pwith

Differential Revision: https://phabricator.apertis.org/D399

tracker/common.py

@@ -111,9 +111,13 @@ class TrackerIndexer():
         self.loop.run()
 
     def assert_indexed(self, path, extra=None):
+        # Select entries for the given URL. Also check that is has the
+        # tracker:extractor-data-source flag added by tracker-extract when
+        # metadata has been extracted.
         query = ('select ?urn where { '
                  '  ?urn nie:url "file://%s" ; '
-                 '  tracker:available true . ') % (path)
+                 '  tracker:available true ; '
+                 '  nie:dataSource tracker:extractor-data-source . ') % (path)
         if extra is not None:
             query += extra
         query += ' }'