DOC: Sync sphinxext with upstream

docs/sphinxext/github_link.py

@@ -2,12 +2,12 @@
 This script comes from scikit-learn:
 https://github.com/scikit-learn/scikit-learn/blob/master/doc/sphinxext/github_link.py
 """
-from operator import attrgetter
 import inspect
-import subprocess
 import os
+import subprocess
 import sys
 from functools import partial
+from operator import attrgetter
 
 REVISION_CMD = "git rev-parse --short HEAD"
 
@@ -44,14 +44,12 @@ def _linkcode_resolve(domain, info, package, url_fmt, revision):
         return
 
     class_name = info["fullname"].split(".")[0]
-    if type(class_name) != str:
-        # Python 2 only
-        class_name = class_name.encode("utf-8")
     module = __import__(info["module"], fromlist=[class_name])
-    try:
-        obj = attrgetter(info["fullname"])(module)
-    except AttributeError:
-        return
+    obj = attrgetter(info["fullname"])(module)
+
+    # Unwrap the object to get the correct source
+    # file in case that is wrapped by a decorator
+    obj = inspect.unwrap(obj)
 
     try:
         fn = inspect.getsourcefile(obj)