This patch was developed in-house, and submitted upstream:
http://bugs.python.org/issue26414
--- Python-2.7.11/Lib/posixpath.py.orig 2015-12-05 11:47:01.000000000 -0800
+++ Python-2.7.11/Lib/posixpath.py 2016-02-14 08:35:25.668221850 -0800
@@ -32,7 +32,7 @@
extsep = '.'
sep = '/'
pathsep = ':'
-defpath = ':/bin:/usr/bin'
+defpath = '/bin:/usr/bin'
altsep = None
devnull = '/dev/null'