I don't think the tests should be moved from one file to the other. It's making more difficult to tell whether you have changed them or not. I think moving the tests (as well as changing the synopsis, hello Eric) are cosmetic changes that are better done in separate changesets.

Some other things:
- please do the "import tempfile" at the top-level. Imports from functions are generally frown upon, unless otherwise necessary.
- instead of "try ... finally: tfp.close()", you can simply write "with tfp: ..."
- I don't understand why `size` is read only when a reporthook is set, while it is always used for raising ContentTooShortError
- I'm not sure why the reporthook is called with `bs` rather than `len(block)`. I think the user is more interested in the actual number of bytes.
- you don't need to update Misc/NEWS yourself