test_multiprocessing: test.support.import_module() does not ignore the ImportError on SemLock

[vstinner]

BPO	18302
Nosy	@brettcannon, @vstinner
Dependencies	bpo-15767: add ModuleNotFoundError

^{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 = 'https://github.com/brettcannon'
closed_at = <Date 2013-07-04.22:45:18.686>
created_at = <Date 2013-06-25.19:06:45.589>
labels = []
title = 'test_multiprocessing: test.support.import_module() does not ignore the ImportError on SemLock'
updated_at = <Date 2013-07-04.22:45:18.685>
user = 'https://github.com/vstinner'

bugs.python.org fields:

activity = <Date 2013-07-04.22:45:18.685>
actor = 'brett.cannon'
assignee = 'brett.cannon'
closed = True
closed_date = <Date 2013-07-04.22:45:18.686>
closer = 'brett.cannon'
components = []
creation = <Date 2013-06-25.19:06:45.589>
creator = 'vstinner'
dependencies = ['15767']
files = []
hgrepos = []
issue_num = 18302
keywords = []
message_count = 3.0
messages = ['191876', '192320', '192321']
nosy_count = 3.0
nosy_names = ['brett.cannon', 'vstinner', 'sbt']
pr_nums = []
priority = 'normal'
resolution = 'out of date'
stage = 'needs patch'
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue18302'
versions = ['Python 3.4']

[vstinner]

test.support.import_module() catchs ModuleNotFoundError instead of ImportError since the following changeset:

changeset: 84106:c4d7228421df
user: Brett Cannon <brett@python.org>
date: Wed Jun 12 20:12:30 2013 -0400
files: Lib/test/regrtest.py Lib/test/support.py Lib/test/test___all__.py Lib/xmlrpc/server.py Lib/zipfile.py
description:
Move test___all__ over to unittest.main() and use ModuleNotFoundError

The problem is that multiprocessing.synchronize raises an ImportError if _multiprocess.SemLock does not exist:

# Try to import the mp.synchronize module cleanly, if it fails
# raise ImportError for platforms lacking a working sem_open implementation.
# See bpo-3770
try:
from X_multiprocessing import SemLock
except (ImportError):
raise ImportError("This platform lacks a functioning sem_open" +
" implementation, therefore, the required" +
" synchronization primitives needed will not" +
" function, see bpo-3770.")

As a result, test_multiprocessing is no more skipped on FreeBSD 6.4, but the following traceback is written:

http://buildbot.python.org/all/builders/x86%20FreeBSD%206.4%203.x/builds/3771/steps/test/logs/stdio

Re-running test 'test_multiprocessing' in verbose mode
test test_multiprocessing crashed -- Traceback (most recent call last):
  File "/usr/home/db3l/buildarea/3.x.bolen-freebsd/build/Lib/multiprocessing/synchronize.py", line 27, in <module>
    from _multiprocessing import SemLock
ModuleNotFoundError: cannot import name SemLock

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/home/db3l/buildarea/3.x.bolen-freebsd/build/Lib/test/regrtest.py", line 1300, in runtest_inner
    the_module = importlib.import_module(abstest)
  File "/usr/home/db3l/buildarea/3.x.bolen-freebsd/build/Lib/importlib/__init__.py", line 93, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 1614, in _gcd_import
  File "<frozen importlib._bootstrap>", line 1595, in _find_and_load
  File "<frozen importlib._bootstrap>", line 1562, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 609, in _check_name_wrapper
  File "<frozen importlib._bootstrap>", line 1058, in load_module
  File "<frozen importlib._bootstrap>", line 928, in load_module
  File "<frozen importlib._bootstrap>", line 274, in _call_with_frames_removed
  File "/usr/home/db3l/buildarea/3.x.bolen-freebsd/build/Lib/test/test_multiprocessing.py", line 30, in <module>
    test.support.import_module('multiprocessing.synchronize')
  File "/usr/home/db3l/buildarea/3.x.bolen-freebsd/build/Lib/test/support.py", line 123, in import_module
    return importlib.import_module(name)
  File "/usr/home/db3l/buildarea/3.x.bolen-freebsd/build/Lib/importlib/__init__.py", line 93, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 1614, in _gcd_import
  File "<frozen importlib._bootstrap>", line 1595, in _find_and_load
  File "<frozen importlib._bootstrap>", line 1562, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 609, in _check_name_wrapper
  File "<frozen importlib._bootstrap>", line 1058, in load_module
  File "<frozen importlib._bootstrap>", line 928, in load_module
  File "<frozen importlib._bootstrap>", line 274, in _call_with_frames_removed
  File "/usr/home/db3l/buildarea/3.x.bolen-freebsd/build/Lib/multiprocessing/synchronize.py", line 32, in <module>
    " function, see issue 3770.")
ImportError: This platform lacks a functioning sem_open implementation, therefore, the required synchronization primitives needed will not function, see issue 3770.

[vstinner]

Brett: Why did you close this issue? It still occurs on the buildbot:

http://buildbot.python.org/all/builders/x86%20FreeBSD%206.4%203.x/builds/3794/steps/test/logs/stdio

[brettcannon]

Because I removed ModuleNotFoundError; check the buildbot again and you will notice it is 8 changesets behind, most of which are related to the removal of ModuleNotFoundError.