* gdb.python/py-prettyprint.py (_iterator): Remove exception_flag

	* gdb.python/py-prettyprint.py (_iterator): Remove exception_flag
	exception.
	(_iterator_except): New function.
	(ArrayPrinter): Use _iterator function instead of local _iterator
	class for Python 3 compatibility.
	(NoStringContainerPrinter): Use _iterator_except instead of
	_iterator.
	* gdb.python/py-typeprint.exp: Use exec(open(...).read()) instead of
	execfile for Python 3 compatibility.
	* gdb.python/python.exp: Handle Python 2.4 exception traceback
	format in error_prompt test.