Review performance of inspect.getfullargspec

GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2019-05-22.12:19:41.727>
labels = ['performance']
title = 'Review performance of inspect.getfullargspec'
updated_at = <Date 2019-05-22.16:13:47.599>
user = 'https://github.com/ncoghlan'

bugs.python.org fields:

activity = <Date 2019-05-22.16:13:47.599>
actor = 'pablogsal'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = []
creation = <Date 2019-05-22.12:19:41.727>
creator = 'ncoghlan'
dependencies = []
files = []
hgrepos = []
issue_num = 37010
keywords = []
message_count = 2.0
messages = ['343186', '343202']
nosy_count = 5.0
nosy_names = ['ncoghlan', 'zzzeek', 'yselivanov', 'hroncok', 'pablogsal']
pr_nums = []
priority = 'normal'
resolution = None
stage = 'needs patch'
status = 'open'
superseder = None
type = 'performance'
url = 'https://bugs.python.org/issue37010'
versions = []