diff -r 262204877004 Doc/library/argparse.rst
--- a/Doc/library/argparse.rst	Mon Apr 14 11:20:45 2014 -0400
+++ b/Doc/library/argparse.rst	Tue Apr 15 11:09:13 2014 -0400
@@ -492,7 +492,10 @@
 :meth:`~ArgumentParser.convert_arg_line_to_args`) and are treated as if they
 were in the same place as the original file referencing argument on the command
 line.  So in the example above, the expression ``['-f', 'foo', '@args.txt']``
-is considered equivalent to the expression ``['-f', 'foo', '-f', 'bar']``.
+is considered equivalent to the expression ``['-f', 'foo', '-f', 'bar']``. By
+default, empty lines in a file are interpreted as empty strings. An empty
+string is not an acceptable argument; but it is an acceptable value for an
+argument.
 
 The ``fromfile_prefix_chars=`` argument defaults to ``None``, meaning that
 arguments will never be treated as file references.
diff -r 262204877004 Lib/argparse.py
--- a/Lib/argparse.py	Mon Apr 14 11:20:45 2014 -0400
+++ b/Lib/argparse.py	Tue Apr 15 11:09:13 2014 -0400
@@ -1717,7 +1717,7 @@
         args, argv = self.parse_known_args(args, namespace)
         if argv:
             msg = _('unrecognized arguments: %s')
-            self.error(msg % ' '.join(argv))
+            self.error(msg % ' '.join(repr(x) for x in argv))
         return args
 
     def parse_known_args(self, args=None, namespace=None):