[Python-Dev] BDFL ruling request: should we block forever waiting for high-quality random bits?

[Random832]

On Thu, Jun 16, 2016, at 04:03, Barry Warsaw wrote:
> *If* we can guarantee that os.urandom() will never block or raise an
> exception when only poor entropy is available, then it may be indeed
> indistinguishably backward compatible for most if not all cases.

Why can't we exclude cases when only poor entropy is available from
"most if not all cases"?