("Forward-port" of r46506)

Remove various dependencies on dictionary order in the standard library
tests, and one (clearly an oversight, potentially critical) in the
standard library itself - base64.py.

Remaining open issues:
 * test_extcall is an output test, messy to make robust
 * tarfile.py has a potential bug here, but I'm not familiar
   enough with this code.  Filed in as SF bug #1496501.
 * urllib2.HTTPPasswordMgr() returns a random result if there is more
   than one matching root path.  I'm asking python-dev for
   clarification...

Lib/optparse.py

@@ -611,8 +611,10 @@ def _set_attrs(self, attrs):
                 else:
                     setattr(self, attr, None)
         if attrs:
+            attrs = attrs.keys()
+            attrs.sort()
             raise OptionError(
-                "invalid keyword arguments: %s" % ", ".join(attrs.keys()),
+                "invalid keyword arguments: %s" % ", ".join(attrs),
                 self)
 
 
@@ -1661,6 +1663,7 @@ def _match_abbrev(s, wordmap):
             raise BadOptionError(s)
         else:
             # More than one possible completion: ambiguous prefix.
+            possibilities.sort()
             raise AmbiguousOptionError(s, possibilities)