old_contents: from proxy import CachingS3Proxy
  
  def application(environ, start_response):
      p = CachingS3Proxy()
      return p.proxy_s3_bucket(environ, start_response)
  
new_contents: import os
  import tempfile
  from proxy import CachingS3Proxy
  
  def application(environ, start_response):
      capacity = int(os.environ.get('CAPACITY', 1000000000))
      cache_dir = os.environ.get('CACHEDIR', tempfile.gettempdir())
      p = CachingS3Proxy(capacity, cache_dir)
      return p.proxy_s3_bucket(environ, start_response)
  
subject: make wsgi app honor vars too