don't assume strings to be byte strings

2 files changed, 3 insertions, 2 deletions

diff --git a/sphinx/pycode/__init__.py b/sphinx/pycode/__init__.py
index b8e2fded..cb9c0887 100644
--- a/sphinx/pycode/__init__.py
+++ b/sphinx/pycode/__init__.py
@@ -98,7 +98,8 @@ class AttrDocVisitor(nodes.NodeVisitor):
             if not pnode or pnode.type not in (token.INDENT, token.DEDENT):
                 break
             prefix = pnode.get_prefix()
-        prefix = prefix.decode(self.encoding)
+        if not isinstance(prefix, unicode):
+            prefix = prefix.decode(self.encoding)
         docstring = prepare_commentdoc(prefix)
         self.add_docstring(node, docstring)
 
diff --git a/sphinx/pycode/pgen2/literals.py b/sphinx/pycode/pgen2/literals.py
index 31900291..d4893702 100644
--- a/sphinx/pycode/pgen2/literals.py
+++ b/sphinx/pycode/pgen2/literals.py
@@ -66,7 +66,7 @@ uni_escape_re = re.compile(r"\\(\'|\"|\\|[abfnrtv]|x.{0,2}|[0-7]{1,3}|"
 def evalString(s, encoding=None):
     regex = escape_re
     repl = escape
-    if encoding:
+    if encoding and not isinstance(s, unicode):
         s = s.decode(encoding)
     if s.startswith('u') or s.startswith('U'):
         regex = uni_escape_re