glob.glob with ** does not always detect symlink loops

GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2021-04-16.20:08:18.994>
labels = ['library', '3.9']
title = 'glob.glob with ** does not always detect symlink loops'
updated_at = <Date 2021-04-16.20:10:06.645>
user = 'https://bugs.python.org/rrt'

bugs.python.org fields:

activity = <Date 2021-04-16.20:10:06.645>
actor = 'rrt'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2021-04-16.20:08:18.994>
creator = 'rrt'
dependencies = []
files = []
hgrepos = []
issue_num = 43875
keywords = []
message_count = 1.0
messages = ['391253']
nosy_count = 1.0
nosy_names = ['rrt']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = None
url = 'https://bugs.python.org/issue43875'
versions = ['Python 3.9']