gistfile1.txt

Instead of:

    try:
        app.memcache.delete(cache_key)
    except AttributeError:
        try:
            env['swift.cache'].delete(cache_key)
        except (KeyError, AttributeError):
            pass

How about:

    memcache = getattr(app, 'memcache', None) or env.get('swift.cache')
    if memcache:
        memcache.delete(cache_key)

Less than half the lines, no try/except overhead (albeit that's tiny), and no
repeated .delete call code.