=== modified file 'mapping.py'
--- mapping.py	2013-09-02 00:54:58 +0000
+++ mapping.py	2016-07-19 00:01:08 +0000
@@ -333,7 +333,11 @@
         if commit is None:
             raise AssertionError("Commit object can't be None")
         if commit.extra:
-            raise UnknownCommitExtra(commit, [item[0] for item in commit.extra])
+            # Loop through looking for extra data that does not apply.
+            for (extra_key, extra_value) in commit.extra:
+                # Ignore GPG Signatures.
+                if extra_key != "gpgsig":
+                    raise UnknownCommitExtra(commit, [item[0] for item in commit.extra])
         rev = ForeignRevision(commit.id, self,
                 self.revision_id_foreign_to_bzr(commit.id))
         rev.git_metadata = None