DOC: Fix creation of [source] links in the doc creation (pandas-dev#23129)

Author: vkk800

doc/source/conf.py

@@ -569,7 +569,11 @@ def linkcode_resolve(domain, info):
             return None
 
     try:
-        fn = inspect.getsourcefile(obj)
+        # inspect.unwrap() was added in Python version 3.4
+        if sys.version_info >= (3, 5):
+            fn = inspect.getsourcefile(inspect.unwrap(obj))
+        else:
+            fn = inspect.getsourcefile(obj)
     except:
         fn = None
     if not fn: