Add similar mock

[RoelantStegmann]

I like this package, but now I need to only disable internet in part of my test - this way I can test if a certain caching method indeed prevents requests to pages, and thus will work when connection fails. I don't find in the docs if this is supported?

def some_test():
    # This runs with internet
    ...

    # This runs without 
    with no_internet:
         .... 

    # This should run with 
    ...