Reject changes with cleanspecs.

Cleanspecs must not be removed once they have been built. This means
they can't be reverted, or reliably cherry-picked. Just skip any
changes that include them since they make such a mess.

Change-Id: I3df8d81f93651d573485de7a75ecf5c6278c0001

tools/bionicbb/gerrit.py

@@ -29,6 +29,12 @@ def get_commit(change_id, revision):
         call('/changes/{}/revisions/{}/commit'.format(change_id, revision)))
 
 
+def get_files_for_revision(change_id, revision):
+    return json.loads(
+        call('/changes/{}/revisions/{}/files'.format(
+            change_id, revision))).keys()
+
+
 def call(endpoint, method='GET'):
     if method != 'GET':
         raise NotImplementedError('Currently only HTTP GET is supported.')