exec something in {} raises an exception

[tjwei]

when o decompile "exec a in {}"
an execption will be raised in EXEC_STMT of simple_instructions.py
at line 562
if getattr(globals_, 'id',) == 'None':

this is because the ast object globals_ does not have an id

[srossross]

The bug fix is in the develop branch. I'll create a new release in a week or so.