Package Manager stops working, says something about packages too old.
And if I tried to update Cabal package index by `cable update`, then I getting the error below:
Downloading the latest package list from stackage-lts-9.6
cabal: Failed to download http://www.stackage.org/lts-9.6/00-index.tar.gz :
HTTP code 308.
I think this caused by that Cabal didn't follow the HTTP redirect.