Centralized documentation of assumptions made by C code

GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2018-03-11.18:17:26.481>
labels = ['docs']
title = 'Centralized documentation of assumptions made by C code'
updated_at = <Date 2018-03-12.06:29:39.491>
user = 'https://github.com/tvanslyke'

bugs.python.org fields:

activity = <Date 2018-03-12.06:29:39.491>
actor = 'benjamin.peterson'
assignee = 'docs@python'
closed = False
closed_date = None
closer = None
components = ['Documentation']
creation = <Date 2018-03-11.18:17:26.481>
creator = 'tvanslyke'
dependencies = []
files = []
hgrepos = []
issue_num = 33050
keywords = []
message_count = 2.0
messages = ['313607', '313634']
nosy_count = 3.0
nosy_names = ['benjamin.peterson', 'docs@python', 'tvanslyke']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = None
url = 'https://bugs.python.org/issue33050'
versions = ['Python 3.6']