Index: Lib/urllib.py
===================================================================
--- Lib/urllib.py	(revision 71734)
+++ Lib/urllib.py	(working copy)
@@ -176,6 +176,9 @@
     def open(self, fullurl, data=None):
         """Use URLopener().open(file) instead of open(file, 'r')."""
         fullurl = unwrap(toBytes(fullurl))
+        # percent encode url, fixing lame server errors for e.g, like space
+        # within url paths.
+        fullurl = quote(fullurl, safe="%/:=&?~#+!$,;'@()*[]")
         if self.tempcache and fullurl in self.tempcache:
             filename, headers = self.tempcache[fullurl]
             fp = open(filename, 'rb')
Index: Lib/test/test_urllib.py
===================================================================
--- Lib/test/test_urllib.py	(revision 71734)
+++ Lib/test/test_urllib.py	(working copy)
@@ -598,6 +598,18 @@
         self.assertEqual(('user', 'a:b'),urllib.splitpasswd('user:a:b'))
 
 
+class URLopener_Tests(unittest.TestCase):
+    """Testcase to test the open method of URLopener class."""
+
+    def test_quoted_open(self):
+        class DummyURLopener(urllib.URLopener):
+            def open_spam(self, url):
+                return url
+
+        self.assertEqual(DummyURLopener().open(
+            'spam://example/ /'),'//example/%20/')
+
+
 # Just commented them out.
 # Can't really tell why keep failing in windows and sparc.
 # Everywhere else they work ok, but on those machines, someteimes
@@ -693,6 +705,7 @@
             urlencode_Tests,
             Pathname_Tests,
             Utility_Tests,
+            URLopener_Tests,
             #FTPWrapperTests,
         )