PyArg_ParseTupleAndKeywords: support required keyword arguments

GitHub fields:

assignee = 'https://github.com/serhiy-storchaka'
closed_at = None
created_at = <Date 2018-07-26.13:04:16.983>
labels = ['interpreter-core', 'type-feature', '3.8']
title = 'PyArg_ParseTupleAndKeywords: support required keyword arguments'
updated_at = <Date 2019-06-08.18:34:20.456>
user = 'https://github.com/serhiy-storchaka'

bugs.python.org fields:

activity = <Date 2019-06-08.18:34:20.456>
actor = 'taleinat'
assignee = 'serhiy.storchaka'
closed = False
closed_date = None
closer = None
components = ['Interpreter Core']
creation = <Date 2018-07-26.13:04:16.983>
creator = 'serhiy.storchaka'
dependencies = []
files = []
hgrepos = []
issue_num = 34235
keywords = ['patch']
message_count = 9.0
messages = ['322419', '322589', '322592', '334736', '335590', '335593', '335666', '335669', '345060']
nosy_count = 4.0
nosy_names = ['taleinat', 'larry', 'serhiy.storchaka', 'msullivan']
pr_nums = ['11834']
priority = 'normal'
resolution = None
stage = 'patch review'
status = 'open'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue34235'
versions = ['Python 3.8']