Class DecimalException

              object --+                
                       |                
exceptions.BaseException --+            
                           |            
        exceptions.Exception --+        
                               |        
        exceptions.StandardError --+    
                                   |    
          exceptions.ArithmeticError --+
                                       |
                                      DecimalException

Known Subclasses:

• Clamped
• , InvalidOperation
• , DivisionByZero
• , Inexact
• , Rounded
• , Subnormal

Base exception class.

Used exceptions derive from this.
If an exception derives from another exception besides this (such as
Underflow (Inexact, Rounded, Subnormal) that indicates that it is only
called if the others are present.  This isn't actually used for
anything, though.

handle  -- Called when context._raise_error is called and the
           trap_enabler is set.  First argument is self, second is the
           context.  More arguments can be given, those being after
           the explanation in _raise_error (For example,
           context._raise_error(NewError, '(-x)!', self._sign) would
           call NewError().handle(context, self._sign).)

To define a new exception, it should be sufficient to have it derive
from DecimalException.