Move to_str alias into ansible.utils.unicode

@abadger suggested on IRC that it's useful enough to go into
ansible.utils.unicode.

lib/ansible/errors/__init__.py

@@ -20,15 +20,7 @@ from __future__ import (absolute_import, division, print_function)
 __metaclass__ = type
 
 from ansible.errors.yaml_strings import *
-from ansible.utils.unicode import to_unicode, to_bytes
+from ansible.utils.unicode import to_unicode, to_str
-
-
-if str is bytes:
-    # Python 2
-    to_str = to_bytes
-else:
-    # Python 3
-    to_str = to_unicode
 
 
 class AnsibleError(Exception):

lib/ansible/utils/unicode.py

@@ -251,3 +251,10 @@ def to_bytes(obj, encoding='utf-8', errors='replace', nonstring=None):
 # ensure that a filter will return unicode values.
 def unicode_wrap(func, *args, **kwargs):
     return to_unicode(func(*args, **kwargs), nonstring='passthru')
+
+
+# Alias for converting to native strings.
+if PY3:
+    to_str = to_unicode
+else:
+    to_str = to_bytes