remove confusing delete indexing (closes #21466)
backport hmac.compare_digest to partially implement PEP 466 (closes #21306)

Backport from Alex Gaynor.
cast away warnings
this file now has utf-8 chars
use logical rather than bit and
Issue #18104: Add idlelib/idle_test/htest.py with a few sample tests to begin
consolidating and improving human-validated tests of Idle. Change other files
as needed to work with htest.  Running the module as __main__ runs all tests.
whitespace