Fix non-string arguments to metadata_check

src/filter.py

@@ -237,6 +237,8 @@ class Filter(object):
         if not self.force_metadata:
             for key in data:
                 wanted = data[key]
+                if not isinstance(wanted, basestring):
+                    wanted = str(wanted)
                 val = metadata.get(key, wanted)
                 # Force UTF-8 encoding for comparison and display
                 wanted = wanted.encode('utf-8')