use UnicodeMixin for __str__, __unicode__ to support py2/py3 in one source. refs #1350.

3 files changed, 20 insertions, 24 deletions

diff --git a/sphinx/domains/cpp.py b/sphinx/domains/cpp.py
index 0b9d3b023..11fe5ad1b 100644
--- a/sphinx/domains/cpp.py
+++ b/sphinx/domains/cpp.py
@@ -22,6 +22,7 @@ from sphinx.domains import Domain, ObjType
 from sphinx.directives import ObjectDescription
 from sphinx.util.nodes import make_refnode
 from sphinx.util.compat import Directive
+from sphinx.util.pycompat import UnicodeMixin
 from sphinx.util.docfields import Field, GroupedField
 
 
@@ -104,19 +105,16 @@ _id_shortwords = {
 }
 
 
-class DefinitionError(Exception):
+class DefinitionError(UnicodeMixin, Exception):
 
     def __init__(self, description):
         self.description = description
 
-    def __str__(self):
-        return text_type(self).encode('utf-8')
-
     def __unicode__(self):
         return self.description
 
 
-class DefExpr(object):
+class DefExpr(UnicodeMixin):
 
     def __eq__(self, other):
         if type(self) is not type(other):
@@ -162,9 +160,6 @@ class DefExpr(object):
         """Prefix a name node (a node returned by :meth:`get_name`)."""
         raise NotImplementedError()
 
-    def __str__(self):
-        return text_type(self).encode('utf-8')
-
     def __unicode__(self):
         raise NotImplementedError()
 
@@ -225,7 +220,7 @@ class PathDefExpr(PrimaryDefExpr):
         return u'::'.join(map(text_type, self.path))
 
 
-class ArrayTypeSuffixDefExpr(object):
+class ArrayTypeSuffixDefExpr(UnicodeMixin):
 
     def __init__(self, size_hint=None):
         self.size_hint = size_hint
diff --git a/sphinx/ext/napoleon/docstring.py b/sphinx/ext/napoleon/docstring.py
index 3993dfeaa..6a6650389 100644
--- a/sphinx/ext/napoleon/docstring.py
+++ b/sphinx/ext/napoleon/docstring.py
@@ -19,6 +19,7 @@ import six
 from six.moves import range
 
 from sphinx.ext.napoleon.iterators import modify_iter
+from sphinx.util.pycompat import UnicodeMixin
 
 
 _directive_regex = re.compile(r'\.\. \S+::')
@@ -26,7 +27,7 @@ _google_untyped_arg_regex = re.compile(r'\s*(\w+)\s*:\s*(.*)')
 _google_typed_arg_regex = re.compile(r'\s*(\w+)\s*\(\s*(.+?)\s*\)\s*:\s*(.*)')
 
 
-class GoogleDocstring(object):
+class GoogleDocstring(UnicodeMixin):
     """Parse Google style docstrings.
 
     Convert Google style docstrings to reStructuredText.
@@ -149,20 +150,6 @@ class GoogleDocstring(object):
             }
         self._parse()
 
-    def __str__(self):
-        """Return the parsed docstring in reStructuredText format.
-
-        Returns
-        -------
-        str
-            UTF-8 encoded version of the docstring.
-
-        """
-        if six.PY3:
-            return self.__unicode__()
-        else:
-            return self.__unicode__().encode('utf8')
-
     def __unicode__(self):
         """Return the parsed docstring in reStructuredText format.
 
diff --git a/sphinx/util/pycompat.py b/sphinx/util/pycompat.py
index 519afe5fe..b3e50474a 100644
--- a/sphinx/util/pycompat.py
+++ b/sphinx/util/pycompat.py
@@ -48,6 +48,13 @@ if six.PY3:
         return six.text_type(tree)
     from html import escape as htmlescape  # >= Python 3.2
 
+    class UnicodeMixin:
+      """Mixin class to handle defining the proper __str__/__unicode__
+      methods in Python 2 or 3."""
+
+      def __str__(self):
+          return self.__unicode__()
+
 else:
     # Python 2
     b = str
@@ -65,6 +72,13 @@ else:
     # use Python 3 name
     from cgi import escape as htmlescape  # 2.6, 2.7
 
+    class UnicodeMixin(object):
+        """Mixin class to handle defining the proper __str__/__unicode__
+        methods in Python 2 or 3."""
+
+        def __str__(self):
+            return self.__unicode__().encode('utf8')
+
 
 def execfile_(filepath, _globals):
     from sphinx.util.osutil import fs_encoding