Remove versionadded from the tutorial, at a location where it produces more questions than it answers.

Also add tests for hashing.

Patch by Brian Brazil.

close subprocess.PIPE file descriptors when the child encounters an
error prior to exec.

used for stdin/stdout/stderr pipes to the child when fork() fails.

when not expected in subprocess.Popen.wait().

handled by Python to not persist after os.fork() in the child process.

Issue #16411: Fix a bug where zlib.decompressobj().flush() might try to access previously-freed memory.

Patch by Serhiy Storchaka.

Additionally, fix a bug where a MemoryError in allocating a bytes object could
leave the decompressor object in an invalid state (with its unconsumed_tail
member being NULL).

Patch by Serhiy Storchaka.

#13301: use ast.literal_eval() instead of eval() in Tools/i18n/msgfmt.py.  Patch by Serhiy Storchaka.

Thanks to Yongzhi Pan.

Patch by Victor Stinner.

Issue #16350: Fix zlib decompressor handling of unused_data with multiple calls to decompress() after EOF.

Patch by Serhiy Storchaka.

#5057: the peepholer no longer optimizes subscription on unicode literals (e.g. u"foo"[0]) in order to produce compatible pyc files between narrow and wide builds.