Index: Lib/os.py
===================================================================
--- Lib/os.py	(revision 60906)
+++ Lib/os.py	(working copy)
@@ -408,8 +408,6 @@
 except NameError:
     pass
 else:
-    import UserDict
-
     # Fake unsetenv() for Windows
     # not sure about os2 here but
     # I'm guessing they are the same.
@@ -423,39 +421,38 @@
         from riscosenviron import _Environ
     elif name in ('os2', 'nt'):  # Where Env Var Names Must Be UPPERCASE
         # But we store them as upper case
-        class _Environ(UserDict.IterableUserDict):
+        class _Environ(dict):
             def __init__(self, environ):
-                UserDict.UserDict.__init__(self)
-                data = self.data
+                dict.__init__(self)
                 for k, v in environ.items():
-                    data[k.upper()] = v
+                    self[k.upper()] = v
             def __setitem__(self, key, item):
                 putenv(key, item)
-                self.data[key.upper()] = item
+                dict.__setitem__(self, key.upper(), item)
             def __getitem__(self, key):
-                return self.data[key.upper()]
+                return dict.__getitem__(self, key.upper())
             try:
                 unsetenv
             except NameError:
                 def __delitem__(self, key):
-                    del self.data[key.upper()]
+                    dict.__delitem__(self, key.upper())
             else:
                 def __delitem__(self, key):
                     unsetenv(key)
-                    del self.data[key.upper()]
+                    dict.__delitem__(self, key.upper())
                 def clear(self):
-                    for key in self.data.keys():
+                    for key in self.keys():
                         unsetenv(key)
-                        del self.data[key]
+                        del self[key]
                 def pop(self, key, *args):
                     unsetenv(key)
-                    return self.data.pop(key.upper(), *args)
+                    return dict.pop(self, key.upper(), *args)
             def has_key(self, key):
-                return key.upper() in self.data
+                return key.upper() in self
             def __contains__(self, key):
-                return key.upper() in self.data
+                return key.upper() in self
             def get(self, key, failobj=None):
-                return self.data.get(key.upper(), failobj)
+                return dict.get(self, key.upper(), failobj)
             def update(self, dict=None, **kwargs):
                 if dict:
                     try:
@@ -476,13 +473,13 @@
                 return dict(self)
 
     else:  # Where Env Var Names Can Be Mixed Case
-        class _Environ(UserDict.IterableUserDict):
+        class _Environ(dict):
             def __init__(self, environ):
-                UserDict.UserDict.__init__(self)
-                self.data = environ
+                dict.__init__(self)
+                self.update(environ)
             def __setitem__(self, key, item):
                 putenv(key, item)
-                self.data[key] = item
+                dict.__setitem__(self, key, item)
             def update(self,  dict=None, **kwargs):
                 if dict:
                     try:
@@ -506,16 +503,14 @@
             else:
                 def __delitem__(self, key):
                     unsetenv(key)
-                    del self.data[key]
+                    dict.__delitem__(self, key)
                 def clear(self):
-                    for key in self.data.keys():
+                    for key in self.keys():
                         unsetenv(key)
-                        del self.data[key]
+                        del self[key]
                 def pop(self, key, *args):
                     unsetenv(key)
-                    return self.data.pop(key, *args)
-            def copy(self):
-                return dict(self)
+                    return dict.pop(self, key, *args)
 
 
     environ = _Environ(environ)