bug #1365984: urllib and data: URLs. Problem was that cStringIO objects cannot be assigned attributes on the fly.

Lib/urllib.py

@@ -556,7 +556,7 @@ class URLopener:
         msg = '\n'.join(msg)
         f = StringIO(msg)
         headers = mimetools.Message(f, 0)
-        f.fileno = None     # needed for addinfourl
+        #f.fileno = None     # needed for addinfourl
         return addinfourl(f, headers, url)
 
 
@@ -813,7 +813,10 @@ class addbase:
         self.read = self.fp.read
         self.readline = self.fp.readline
         if hasattr(self.fp, "readlines"): self.readlines = self.fp.readlines
-        if hasattr(self.fp, "fileno"): self.fileno = self.fp.fileno
+        if hasattr(self.fp, "fileno"):
+            self.fileno = self.fp.fileno
+        else:
+            self.fileno = lambda: None
         if hasattr(self.fp, "__iter__"):
             self.__iter__ = self.fp.__iter__
             if hasattr(self.fp, "next"):

Misc/NEWS

@@ -287,6 +287,8 @@ Extension Modules
 Library
 -------
 
+- Bug #1365984: urllib now opens "data:" URLs again.
+
 - Patch #1314396: prevent deadlock for threading.Thread.join() when an exception
   is raised within the method itself on a previous call (e.g., passing in an
   illegal argument)