python 3.7 inside venv tries to write back to read-only installation directory (Grammar3.7.0.final.0.pickle)

GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2018-07-25.14:22:36.505>
labels = ['3.7', 'expert-installation']
title = 'python 3.7 inside venv tries to write back to read-only installation directory (Grammar3.7.0.final.0.pickle)'
updated_at = <Date 2019-07-21.07:48:19.682>
user = 'https://github.com/zopyx'

bugs.python.org fields:

activity = <Date 2019-07-21.07:48:19.682>
actor = 'ajung'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Installation']
creation = <Date 2018-07-25.14:22:36.505>
creator = 'ajung'
dependencies = []
files = []
hgrepos = []
issue_num = 34224
keywords = []
message_count = 3.0
messages = ['322357', '322364', '348229']
nosy_count = 2.0
nosy_names = ['ajung', 'xtreak']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = None
url = 'https://bugs.python.org/issue34224'
versions = ['Python 3.7']