os.path.ismount returns false for disconnected CIFS mounts in Linux

GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2019-08-15.23:08:33.383>
labels = ['type-bug']
title = 'os.path.ismount returns false for disconnected CIFS mounts in Linux'
updated_at = <Date 2019-08-15.23:08:33.383>
user = 'https://bugs.python.org/MattChristopher'

bugs.python.org fields:

activity = <Date 2019-08-15.23:08:33.383>
actor = 'Matt Christopher'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = []
creation = <Date 2019-08-15.23:08:33.383>
creator = 'Matt Christopher'
dependencies = []
files = []
hgrepos = []
issue_num = 37870
keywords = []
message_count = 1.0
messages = ['349833']
nosy_count = 1.0
nosy_names = ['Matt Christopher']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue37870'
versions = ['Python 3.6']