Richard Jones' Log: Distutils MANIFEST checking

So it turns out that some programs don't unpack distutils tarballs correctly. My test runner now executes the following code:

def check_manifest():
    """Check that the files listed in the MANIFEST are present when the
    source is unpacked.
    """
    try:
        f = open('MANIFEST')
    except:
        print '\n*** SOURCE ERROR: The MANIFEST file is missing!'
        sys.exit(1)
    try:
        manifest = [l.strip() for l in f.readlines()]
    finally:
        f.close()
    err = [line for line in manifest if not os.path.exists(line)]
    if err:
        n = len(manifest)
        print '\n*** SOURCE ERROR: There are files missing (%d/%d found)!'%(
            n-len(err), n)
        sys.exit(1)

Distutils doesn't automatically check the files unpacked from a source distribution against the packaged MANIFEST. I'm not sure that it could, without potentially breaking some of the other distribution mechanisms. This uncertainty comes from having no clue as to how I could make it run this function when someone tries to install Roundup from source... Anyone? :)

Update: I believe the following is safe. Instead of checking the manifest at install time, I check it at build time:

from distutils.command.build import build

class build_roundup(build):
    def run(self):
        check_manifest()
        build.run(self)

later:

setup(
    ...
    cmdclass = {
        'build': build_roundup,
    },
)