inspecting a partial with bound keywords gives incorrect signature

GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2020-02-25.18:42:14.557>
labels = ['3.8', 'library']
title = 'inspecting a partial with bound keywords gives incorrect signature'
updated_at = <Date 2020-03-02.07:30:17.579>
user = 'https://github.com/cjw296'

bugs.python.org fields:

activity = <Date 2020-03-02.07:30:17.579>
actor = 'cjw296'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2020-02-25.18:42:14.557>
creator = 'cjw296'
dependencies = []
files = []
hgrepos = []
issue_num = 39753
keywords = []
message_count = 4.0
messages = ['362656', '362657', '363084', '363132']
nosy_count = 3.0
nosy_names = ['cjw296', 'donovick', 'Ido Michael']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = None
url = 'https://bugs.python.org/issue39753'
versions = ['Python 3.8']