Add ability to inherit unittest argument parser

GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2020-01-10.04:32:18.746>
labels = ['type-bug', 'library']
title = 'Add ability to inherit unittest arguement parser'
updated_at = <Date 2020-01-21.10:12:39.221>
user = 'https://github.com/httpsgithubcomatb00ker'

bugs.python.org fields:

activity = <Date 2020-01-21.10:12:39.221>
actor = 'atb00ker'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2020-01-10.04:32:18.746>
creator = 'atb00ker'
dependencies = []
files = []
hgrepos = []
issue_num = 39283
keywords = []
message_count = 5.0
messages = ['359704', '359716', '359949', '360226', '360381']
nosy_count = 3.0
nosy_names = ['paul.j3', 'xtreak', 'atb00ker']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue39283'
versions = []