Fix bug in copy() by using copy.copy() instead of making assumptions

(it so happens that copy.copy() works fine for the base UserDict
type).  Also reindented the entire module to have 4-space indents.

Lib/UserDict.py

 # A more or less complete user-defined wrapper around dictionary objects
 
 class UserDict:
-	def __init__(self): self.data = {}
-	def __repr__(self): return repr(self.data)
-	def __cmp__(self, dict):
-		if type(dict) == type(self.data):
-			return cmp(self.data, dict)
-		else:
-			return cmp(self.data, dict.data)
-	def __len__(self): return len(self.data)
-	def __getitem__(self, key): return self.data[key]
-	def __setitem__(self, key, item): self.data[key] = item
-	def __delitem__(self, key): del self.data[key]
-	def clear(self): return self.data.clear()
-	def copy(self):
-	    if self.__class__ is UserDict:
-		new = UserDict()
-		new.dict = self.data.copy()
-	    else:
-		new = self.__class__()	# XXX assumption: constructor signature
-		for k, v in self.items():
-		    new[k] = v
-	    return new
-	def keys(self): return self.data.keys()
-	def items(self): return self.data.items()
-	def values(self): return self.data.values()
-	def has_key(self, key): return self.data.has_key(key)
-	def update(self, other):
-	    if type(other) is type(self.data):
-		self.data.update(other)
-	    else:
-		for k, v in other.items():
-		    self.data[k] = v
+    def __init__(self): self.data = {}
+    def __repr__(self): return repr(self.data)
+    def __cmp__(self, dict):
+	if type(dict) == type(self.data):
+	    return cmp(self.data, dict)
+	else:
+	    return cmp(self.data, dict.data)
+    def __len__(self): return len(self.data)
+    def __getitem__(self, key): return self.data[key]
+    def __setitem__(self, key, item): self.data[key] = item
+    def __delitem__(self, key): del self.data[key]
+    def clear(self): return self.data.clear()
+    def copy(self):
+	import copy
+	return copy.copy(self)
+    def keys(self): return self.data.keys()
+    def items(self): return self.data.items()
+    def values(self): return self.data.values()
+    def has_key(self, key): return self.data.has_key(key)
+    def update(self, other):
+	if type(other) is type(self.data):
+	    self.data.update(other)
+	else:
+	    for k, v in other.items():
+		self.data[k] = v