Exceprtion hierarchy
Object +--Exception +--NoMemoryError +--ScriptError | +--LoadError | +--NotImplementedError | +--SyntaxError +--SecurityError # Was a StandardError in 1.8 +--SignalException | +--Interrupt +--SystemExit +--SystemStackError # Was a StandardError in 1.8 +--StandardError +--ArgumentError +--FiberError # New in 1.9 +--IOError | +--EOFError +--IndexError | +--KeyError # New in 1.9 | +--StopIteration # New in 1.9 +--LocalJumpError +--NameError | +--NoMethodError +--RangeError | +--FloatDomainError +--RegexpError +--RuntimeError +--SystemCallError +--ThreadError +--TypeError +--ZeroDivisionError