Issue 14814: Explain how to get more error detail in the ipaddress tutorial, and tweak the display for octet errors in IPv4 (noticed the formatting problem when adding to the docs)

Issue 14814: Make the ipaddress code easier to follow by using newer language features (patch by Serhiy Storchaka)

Issue 14814: Provide more informative error messages in ipaddress, and ensure that errors are caught as expected

Issue 14814: %s implies coercion with str() - remove a lot of redundant str() calls from the ipaddress implementation

Issue 14814: Eliminate bytes warnings from ipaddress by correctly throwing an exception early when given bytes data of the wrong length. Also removes 2.x backwards compatibility code from associated tests.

Issue 14814: Better handling of cases where octet/hextet parsing fails, including ensuring that tracebacks are still clean even when calling class constructors directly

Issue #15020: The program name used to search for Python's path is now python3 under Unix, not python.

Issue #15020: The program name used to search for Python's path is now "python3" under Unix, not "python".

Fix issue # 15033 - Return the proper exitcode for failure when modules are invoked using -m switch. Patch contributed by Jeff Knupp

Fix issue # 15033 - Return the proper exitcode for failure when modules are invoked using -m switch. Patch contributed by Jeff Knupp

working without _frozen_importlib by moving to an import over a direct
access in sys.modules.

Closes #14902: Fixed timezone conversion of a date/time in the past. Thanks to Yuriy Syrovetskiy for the report and Juancarlo Añez for the patch on which this fix is based.