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/lib/context_managers.py

@@ -2,6 +2,8 @@
 Context managers, i.e. things you can use with the 'with' statement.
 """
 
+from __future__ import absolute_import
+
 import fcntl
 from os import path
 from contextlib import contextmanager