Python 3: shlex.split() wants unicode

On Python 2, shlex.split() raises if you pass it a unicode object with
non-ASCII characters in it.  The Ansible codebase copes by explicitly
converting the string using to_bytes() before passing it to
shlex.split().

On Python 3, shlex.split() raises ('bytes' object has no attribute 'read')
if you pass a bytes object.  Oops.

This commit introduces a new wrapper function, shlex_split, that
transparently performs the to_bytes/to_unicode conversions only on
Python 2.

Currently I've only converted one call site (the one that was causing a
unit test to fail on Python 3).  If this approach is deemed suitable,
I'll convert them all.

test/units/utils/test_shlex.py

@@ -0,0 +1,39 @@
+# (c) 2015, Marius Gedminas <marius@gedmin.as>
+#
+# This file is part of Ansible
+#
+# Ansible is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# Ansible is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with Ansible.  If not, see <http://www.gnu.org/licenses/>.
+
+import unittest
+
+from ansible.utils.shlex import shlex_split
+
+
+class TestSplit(unittest.TestCase):
+
+    def test_trivial(self):
+        self.assertEqual(shlex_split("a b c"), ["a", "b", "c"])
+
+    def test_unicode(self):
+        self.assertEqual(shlex_split(u"a b \u010D"), [u"a", u"b", u"\u010D"])
+
+    def test_quoted(self):
+        self.assertEqual(shlex_split('"a b" c'), ["a b", "c"])
+
+    def test_comments(self):
+        self.assertEqual(shlex_split('"a b" c # d', comments=True), ["a b", "c"])
+
+    def test_error(self):
+        self.assertRaises(ValueError, shlex_split, 'a "b')
+