Code review comment for lp:~sergiusens/account-polld/twitter_avatar

My main concerns with this are:

1. there is no cache eviction, so it will continue to grow unchecked. There is nothing in the push notifications model to tell account-polld when the image isn't needed any more either, so it's not clear how this can be handled reliably.

2. there is no cache validation, so if new avatar images are served from the same URL we will never notice that change.

And if using URIs for icons doesn't work, how exactly will real push notifications provide icons once we have them?