Contributed by Bradley Laney.

Follow up from https://github.com/python/peps/pull/712#issuecomment-403591108:

"people using the repo without using GitHub still ought to be reminded of the COC" - GvR

* When doing getattr lookups with a default of "None", it now
  uses an "is" comparison against None which is more correct
* Removed outdated code

Patch by Brandon Rhodes.

Initial patch by Joshua Jay Herman.

Fixed also testing the "always" warning filter.

Include a more easily understood example for nullcontext

This will prevent emitting a resource warning when the execution was
interrupted by Ctrl-C between calling open() and entering a 'with' block
in "with open()".

webbrowser._synthesize() called webbrowser.register() with
outdated signature.
Co-Authored-By: John Still <john@jmsdvl.com>

Make the change where discussing the CPython implementation of lists and dicts.

The 'output formatting' section of the tutorial talks a lot about manual formatting with things like .rjust() and .zfill(), with only a passing reference to 3.6's new f-strings.

This doesn't drop all of the old material, but it does rearrange the topics into a more modern order: f-strings first, discussing formatting specifiers a bit; then calling .format(); finally manual formatting with .ljust().

"can be used do declare" → "can be used to declare"

* Always return bytes from _HackedGetData.get_data().

Ensure the imp.load_source shim always returns bytes by reopening the file in
binary mode if needed. Hash-based pycs have to receive the source code in bytes.

It's tempting to change imp.get_suffixes() to always return 'rb' as a mode, but
that breaks some stdlib tests and likely 3rdparty code, too.

Stop using key=lambda.  This behavior is same to C version encoder.

The multiprocessing module now uses the monotonic clock
time.monotonic() instead of the system clock time.time() to implement
timeouts.

* converted bytes methods: expandtabs, ljust, rjust, center, zfill
* updated char_convertor to properly set the C default value

The line is speaking of a list of commands, not the list command.