Issue1847091

Let's create file:
---qq.py
import sys
if hasattr(sys, 'exit'):
  print 'first if'
  del sys.exit
if hasattr(sys, 'exit'):
  print 'second if'
  del sys.exit
print 'done'
---cut
Now let's run it in standard python:
# python qq.py
first if
done
And now in jython:
# jython qq.py
first if
second if
Traceback (innermost last):
  File "qq.py", line 7, in ?
KeyError: exit

Example from standard library:
  # jython Lib/site.py
should output sys.path, but failes with following error:
  Traceback (innermost last):
    File "Lib\site.py", line 254, in ?
  KeyError: setdefaultencoding

Only applied to attributes of sys (PySystemState) due to its special way
it's implemented to look like a regular module.
Fixed in 2.5 by r5185
Tested by test_sys.py and test_sys_jy.py