Add missing py-contextlib2 (#13056)

Change-Id: I8e0a90d4aa2c9f46230a6fe35ce5f4fa44672faf

var/spack/repos/builtin/packages/py-contextlib2/package.py

@@ -0,0 +1,20 @@
+# Copyright 2013-2019 Lawrence Livermore National Security, LLC and other
+# Spack Project Developers. See the top-level COPYRIGHT file for details.
+#
+# SPDX-License-Identifier: (Apache-2.0 OR MIT)
+
+
+from spack import *
+
+
+class PyContextlib2(PythonPackage):
+    """contextlib2 is a backport of the standard library's contextlib module to
+    earlier Python versions."""
+
+    homepage = "https://contextlib2.readthedocs.io/en/stable/"
+    url      = "https://github.com/jazzband/contextlib2/archive/v0.6.0.tar.gz"
+
+    version('0.6.0', sha256='4f18e2f28bb642aae9447aacec93b1319c8ee838711553c0a2bd906753f2ad33')
+
+    depends_on('py-setuptools', type='build')
+    depends_on('python@2.7:2.8,3.4:', type=('build', 'run'))