Enable absolute imports.

See PEP 328[1] for details. This feature was introduced in Python 2.5 and
will become mandatory in Python 3.

[1]: http://www.python.org/dev/peps/pep-0328

(imported from commit 7444eeba8a08d5f91b94c7921848f2274979bd76)

zephyr/retention_policy.py

@@ -9,6 +9,7 @@ rather than iterating through messages one by one.
 The code in this module does not actually remove anything; it just identifies
 which items should be kept or removed.
 """
+from __future__ import absolute_import
 
 import operator