change a file with a context manager

[Andrea Crotti]

So I have the following problem, I need something to copy a file to a 
certain position
and restore it after.
So I wrote this simple context manager:

class WithCorrectEasyInstall(object):

     def __enter__(self):
         import pkg_resources
         from shutil import copyfile
         easy_install_file = 
pkg_resources.resource_filename('psi.devsonly', 'windows_easy_install.pth')
         self.global_easy_install = 
'c:/python25/Lib/site-packages/easy-install.pth'
         # can use mmap, a temporary file or just write to string
         self.stored = open(self.global_easy_install).read()
         logger.debug("copying the correct easy_install.pth file to the 
global position")
         copyfile(easy_install_file, self.global_easy_install)

     def __exit__(self, type, value, traceback):
         #TODO: make sure it's restored also when quitting in some other 
ways
         # restore the old file
         open(self.global_easy_install, 'w').write(self.stored)
         logger.debug("restoring the old easy_install.pth file")


The problem is that this is not executed for example when the program is 
interrupted
with for example a KeyboardInterrupt.
But that's also an exception, why is it not caught by the context manager?

And if there are better way to do what I'm trying to achieve they are 
welcome :)