make an ascii docstring

workaround bundled numpydoc issue

IPython/utils/io.py

@@ -288,14 +288,14 b' class capture_output(object):'
         sys.stderr = self.sys_stderr
 
 def unicode_std_stream(stream='stdout'):
-    u"""Get a wrapper to write unicode to stdout/stderr as UTF-8.
+    r"""Get a wrapper to write unicode to stdout/stderr as UTF-8.
 
     This ignores environment variables and default encodings, to reliably write
     unicode to stdout or stderr.
 
     ::
 
-        unicode_std_stream().write(u'ł@e¶ŧ←')
+        unicode_std_stream().write(u'\u0142@e\xb6\u0167\u2190')
     """
     assert stream in ('stdout', 'stderr')
     stream  = getattr(sys, stream)