diff -r 6d278f426417 Doc/library/urllib.request.rst
--- a/Doc/library/urllib.request.rst	Fri Jul 05 18:05:29 2013 -1000
+++ b/Doc/library/urllib.request.rst	Sat Jul 06 11:58:29 2013 +0200
@@ -170,6 +170,11 @@
 
    *url* should be a string containing a valid URL.
 
+   .. versionchanged:: 3.4.0
+      If the *url* string contains any whitespace characters (spaces, tabs,
+      newlines or carriage-returns), they will be quoted using
+      :func:`urllib.parse.quote`. No other characters will be converted.
+
    *data* must be a bytes object specifying additional data to send to the
    server, or ``None`` if no such data is needed.  Currently HTTP requests are
    the only ones that use *data*; the HTTP request will be a POST instead of a
diff -r 6d278f426417 Lib/test/test_urllib.py
--- a/Lib/test/test_urllib.py	Fri Jul 05 18:05:29 2013 -1000
+++ b/Lib/test/test_urllib.py	Sat Jul 06 11:58:29 2013 +0200
@@ -1391,6 +1391,12 @@
         request.method = 'HEAD'
         self.assertEqual(request.get_method(), 'HEAD')
 
+    def test_url_path_space_encoding(self):
+        Request = urllib.request.Request
+        request = Request("http://www.python.org/a b\tc\nd\re")
+        self.assertEqual(request.selector, "/a%20b%09c%0Ad%0De")
+        request = Request("http://www.python.org/a%20b%09c%0Ad%0De")
+        self.assertEqual(request.selector, "/a%20b%09c%0Ad%0De")
 
 class URL2PathNameTests(unittest.TestCase):
 
diff -r 6d278f426417 Lib/urllib/parse.py
--- a/Lib/urllib/parse.py	Fri Jul 05 18:05:29 2013 -1000
+++ b/Lib/urllib/parse.py	Sat Jul 06 11:58:29 2013 +0200
@@ -859,7 +859,7 @@
     """splithost('//host[:port]/path') --> 'host[:port]', '/path'."""
     global _hostprog
     if _hostprog is None:
-        _hostprog = re.compile('^//([^/?]*)(.*)$')
+        _hostprog = re.compile('^//([^/?]*)(.*)$', re.DOTALL)
 
     match = _hostprog.match(url)
     if match:
diff -r 6d278f426417 Lib/urllib/request.py
--- a/Lib/urllib/request.py	Fri Jul 05 18:05:29 2013 -1000
+++ b/Lib/urllib/request.py	Sat Jul 06 11:58:29 2013 +0200
@@ -317,6 +317,8 @@
         self.host, self.selector = splithost(rest)
         if self.host:
             self.host = unquote(self.host)
+        self.selector = re.sub(r'\s', lambda m: quote(m.group()),
+            self.selector)
 
     def get_method(self):
         """Return a string indicating the HTTP request method."""