urllib.request.ProxyHandler works with bad proxy

[spacedog]

I'm using urllib.request to read pages for scraping. Things were connecting and reading OK but I wanted to add some exception handling in-case one of my rotating proxies was bad. So I made a bad proxy to test:
'1.1.1.1:3'

and expected things to fail... but it succeeded instead. Hmmm. Ok, then I used 'xxxx' as he proxy and it still pulled the page - so clearly I'm doing things wrong. I tried to use Fiddler so see if it was using my IP and port instead but I could not see that info in Fiddler. Here's my code:

proxy_handler = urllib.request.ProxyHandler({'http': 'xxxx'})  # 'xxxx' was '161.35.4.201:80'
opener = urllib.request.build_opener(proxy_handler)
opener.addheaders = [('User-agent', 'Mozilla/5.0')]
urllib.request.install_opener(opener)  
page = urllib.request.urlopen(self.url)
data = page.read()

What's the point of urllib.request.ProxyHandler if it doesn't use the proxy I pass into it?

Any help would be great. Thanks.