test_pydoc test_synopsis_sourceless is a flaky test

[gpshead]

BPO	22910
Nosy	@gpshead, @ericsnowcurrently, @koobs, @iritkatriel

^{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 2021-12-07.18:02:31.070>
created_at = <Date 2014-11-21.07:03:41.765>
labels = ['type-bug', 'tests']
title = 'test_pydoc test_synopsis_sourceless is a flaky test'
updated_at = <Date 2021-12-07.18:02:31.069>
user = 'https://github.com/gpshead'

bugs.python.org fields:

activity = <Date 2021-12-07.18:02:31.069>
actor = 'gregory.p.smith'
assignee = 'none'
closed = True
closed_date = <Date 2021-12-07.18:02:31.070>
closer = 'gregory.p.smith'
components = ['Tests']
creation = <Date 2014-11-21.07:03:41.765>
creator = 'gregory.p.smith'
dependencies = []
files = []
hgrepos = []
issue_num = 22910
keywords = []
message_count = 3.0
messages = ['231465', '231469', '407937']
nosy_count = 4.0
nosy_names = ['gregory.p.smith', 'eric.snow', 'koobs', 'iritkatriel']
pr_nums = []
priority = 'normal'
resolution = 'out of date'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue22910'
versions = ['Python 3.4']

[gpshead]

When running a parallel make -j12 test, test_pydoc fails reasonably often with:

test test_pydoc failed -- Traceback (most recent call last):
  File "/.../Lib/test/test_pydoc.py", line 556, in test_synopsis_sourceless   
    synopsis = pydoc.synopsis(filename)
  File "/.../Lib/pydoc.py", line 240, in synopsis
    mtime = os.stat(filename).st_mtime
FileNotFoundError: [Errno 2] No such file or directory: '/.../Lib/__pycache__/os.cpython-34.pyc'

Two other issues mention this failure as being introduced recently in comments:
http://bugs.python.org/issue20123 & http://bugs.python.org/issue20128

[gpshead]

I suspect flakiness is due to parallel test execution. Is some other test possibly executing at the same time removing __pycache__ directories or .pyc files to recreate them (test_compileall?)? If the test were adjusted to point to a .py file of its own that it generates in a temporary directory that would avoid that.

[iritkatriel]

Shall we close this? It's pretty old and if the test is still flaky it will let us know.