traceback when exiting on read-only file system

[zbysz]

BPO	41193
Nosy	@vstinner, @miss-islington
PRs	bpo-41193: Ignore OSError in readline write_history() #21279 [3.9] bpo-41193: Ignore OSError in readline write_history() (GH-21279) #21280 [3.8] bpo-41193: Ignore OSError in readline write_history() (GH-21279) #21281

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2020-07-02.11:07:04.104>
created_at = <Date 2020-07-02.09:13:51.247>
labels = ['3.8', 'library', '3.9', '3.10']
title = 'traceback when exiting on read-only file system'
updated_at = <Date 2020-07-02.12:13:19.269>
user = 'https://bugs.python.org/zbysz'

bugs.python.org fields:

activity = <Date 2020-07-02.12:13:19.269>
actor = 'vstinner'
assignee = 'none'
closed = True
closed_date = <Date 2020-07-02.11:07:04.104>
closer = 'vstinner'
components = ['Library (Lib)']
creation = <Date 2020-07-02.09:13:51.247>
creator = 'zbysz'
dependencies = []
files = []
hgrepos = []
issue_num = 41193
keywords = ['patch']
message_count = 7.0
messages = ['372832', '372840', '372845', '372846', '372847', '372848', '372849']
nosy_count = 4.0
nosy_names = ['vstinner', 'zbysz', 'asottile', 'miss-islington']
pr_nums = ['21279', '21280', '21281']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue41193'
versions = ['Python 3.8', 'Python 3.9', 'Python 3.10']

[zbysz]

[Originally reported as https://bugzilla.redhat.com/show_bug.cgi?id=1852941.]

$ touch ~/foo
touch: cannot touch '/home/fedora/foo': Read-only file system
$ python
Python 3.9.0b3 (default, Jun 10 2020, 00:00:00) 
[GCC 10.1.1 20200507 (Red Hat 10.1.1-1)] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> ^D
Error in atexit._run_exitfuncs:
Traceback (most recent call last):
  File "/usr/lib64/python3.9/site.py", line 462, in write_history
    readline.write_history_file(history)
OSError: [Errno 30] Read-only file system

Looking at /usr/lib64/python3.9/site.py, it already silently skips
PermissionError. If a user is running with the file system in ro mode,
they almost certainly are aware of the fact, since this is done either
on purpose or as a result of disk corruption, and the traceback from
python is not useful. Suppression of PermissionError was added in b249966.

Version-Release number of selected component (if applicable):
python3-3.9.0~b3-1.fc33.x86_64

[vstinner]

New changeset 0ab917e by Victor Stinner in branch 'master':
bpo-41193: Ignore OSError in readline write_history() (GH-21279)
0ab917e

[miss-islington]

New changeset 53d2b71 by Miss Islington (bot) in branch '3.8':
bpo-41193: Ignore OSError in readline write_history() (GH-21279)
53d2b71

[miss-islington]

New changeset 0b4c87e by Miss Islington (bot) in branch '3.9':
bpo-41193: Ignore OSError in readline write_history() (GH-21279)
0b4c87e

[vstinner]

Thanks Zbyszek for your bug report. It's now fixed in 3.8, 3.9 and master branches.

[zbysz]

Wow, that was quick. Thanks!

[vstinner]

Well, two errors were already ignored (bpo-19891). I just made the "except" more generic. I don't think that we can do anything more useless than ignoring the error if the filesystem is read-only. I don't think that a warning would be useful.