ui: use try..finally in configoverride
@contextmanager almost always have their "yield" inside a try..finally
block. This is because if the calling code inside the activated
context manager raises, the code after the "yield" won't get
executed. A "finally" block, however, will get executed in this
scenario.
util: limit output chunk size in zlib decompression
This is essentially a port of
65bd4b8e48bd, which was inadvertently
dropped by
8cd7d0fefd30.