Make _load_testfile() use its encoding argument when __loader__ is defined.

Lib/doctest.py

@@ -209,7 +209,8 @@ def _load_testfile(filename, package, module_relative, encoding):
         filename = _module_relative_path(package, filename)
         if hasattr(package, '__loader__'):
             if hasattr(package.__loader__, 'get_data'):
-                return package.__loader__.get_data(filename).decode('utf-8'), filename
+                return (package.__loader__.get_data(filename).decode(encoding),
+                        filename)
     return open(filename, encoding=encoding).read(), filename
 
 def _indent(s, indent=4):

Misc/NEWS

@@ -14,6 +14,14 @@ Extension Modules
 - The `hotshot` profiler has been removed; use `cProfile` instead.
 
 
+Library
+-------
+
+- When loading an external file using testfile(), the passed-in encoding
+  argument was being ignored if __loader__ is defined and forcing the source to
+  be UTF-8.
+
+
 What's New in Python 3.0a1?
 ==========================