Mismatch between the manipulation of `sys.path` by `runpy` and by the Python command-line interface

GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2020-09-19.15:43:58.546>
labels = ['3.8', 'type-bug', 'library']
title = 'Mismatch between the manipulation of `sys.path` by `runpy` and by the Python command-line interface'
updated_at = <Date 2020-09-19.15:43:58.546>
user = 'https://github.com/maggyero'

bugs.python.org fields:

activity = <Date 2020-09-19.15:43:58.546>
actor = 'maggyero'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2020-09-19.15:43:58.546>
creator = 'maggyero'
dependencies = []
files = []
hgrepos = []
issue_num = 41814
keywords = []
message_count = 1.0
messages = ['377171']
nosy_count = 2.0
nosy_names = ['ncoghlan', 'maggyero']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue41814'
versions = ['Python 3.8']