Marc-Andre Lemburg: Add UnicodeError, derived from ValueError.

Lib/exceptions.py

@@ -61,6 +61,9 @@ Exception(*)
       |    +-- FloatingPointError
       |
       +-- ValueError
+      |    |
+      |    +-- UnicodeError(*)
+      |
       +-- SystemError
       +-- MemoryError
 """
@@ -224,6 +227,10 @@ class UnboundLocalError(NameError):
     """Local name referenced but not bound to a value."""
     pass
 
+class UnicodeError(ValueError):
+    """Unicode related error."""
+    pass
+
 class MemoryError(StandardError):
     """Out of memory."""
     pass