AppEngine fetch through a free proxy
Probably the correct approach is to request permission from the owners of the site you are scraping. 
Even if you use a proxy, there is still a big chance that requests coming through the proxy will end up blocked as well.
My (Python) AppEngine program fetches a web page from another site to scrape data from it -- but it seems like the 3rd party site is blocking requests from Google App Engine! -- I can fetch the page from development mode, but not when deployed.
Can I get around this by using a free proxy of some sort?
Can I use a free proxy to hide the fact that I am requesting from App Engine?
How do I find/choose a proxy? -- what do I need?  --  how do I perform the fetch?
Is there anything else I need to know or watch out for?