Issue #20021: use importlib.machinery to import Lib/opcode.py and not an opcode
module coming from somewhere else. makeopcodetargets.py is part of the Python
build process and it is run by an external Python program, not the built Python
program.

Patch written by Serhiy Storchaka.

Serhiy asked me to review it.

* Replace get/restore methods with a Resource class and Resource subclasses
* Create ModuleAttr, ModuleAttrList and ModuleAttrDict helper classes
* Use __subclasses__() to get resource classes instead of using an hardcoded
  list (2 shutil resources were missinged in the list!)
* Don't define MultiprocessingProcessDangling resource if the multiprocessing
  module is missing
* Nicer diff for dictionaries. Useful for the big os.environ dict
* Reorder code to group resources

tag: tip
parent: 100742:ebae81b31cf6
user: Victor Stinner <victor.stinner@gmail.com>
date: Fri Mar 25 15:03:34 2016 +0100
files: Lib/test/test_os.py
description:
test_os: Win32ErrorTests checks if file exists

Don't use os.path.exists() since it ignores *any* OSError.

Write the module name rather than <module> in the error message, if module has
no __file__ attribute (ex: package).

Issue #26610.

* Simply use "import opcode" to import the opcode module instead of tricks
  using the imp module
* Use context manager for the output file
* Move code into a new main() function
* Replace assert with a regular if to check the number of arguments
* Import modules at top level

Replace also other open(filename, "w") with open(filename, "x") to fail if a
previous test forgot to remove filename.

Changes were backported (transplated) from default to 3.5.

Use -Wd comment line option to log the ResourceWarning.

* multiprocessing: open file with closefd=False to avoid ResourceWarning
* _test_multiprocessing: open file with O_EXCL to detect bugs in tests (if a
  previous test forgot to remove TESTFN)
* test_sys_exit(): remove TESTFN after each loop iteration

Initial patch written by Serhiy Storchaka.

Use -Wd comment line option to log the ResourceWarning.

* multiprocessing: open file with closefd=False to avoid ResourceWarning
* _test_multiprocessing: open file with O_EXCL to detect bugs in tests (if a
  previous test forgot to remove TESTFN)
* test_sys_exit(): remove TESTFN after each loop iteration

Initial patch written by Serhiy Storchaka.

The import machinery now raises a different exception when it fails at Python
shutdown.

Patch by Oren Milman.

Declare the function even if thread support is disabled.

Issue #26637: The importlib module now emits an ImportError rather than a
TypeError if __import__() is tried during the Python shutdown process but
sys.path is already cleared (set to None).

Issue #21925: warnings.formatwarning() now catches exceptions when calling
linecache.getline() and tracemalloc.get_object_traceback() to be able to log
ResourceWarning emitted late during the Python shutdown process.

Issue #21925: warnings.formatwarning() now catches exceptions on
linecache.getline(...) to be able to log ResourceWarning emitted late during
the Python shutdown process.

test_warnings: only run test_improper_option() and test_warnings_bootstrap()
once. The unit test doesn't depend on self.module.

* Rename libregrtest.main_in_temp_cwd() to libregrtest.main()
* Add regrtest.main_in_temp_cwd() alias to libregrtest.main()
* Move old main_in_temp_cwd() code into libregrtest.Regrtest.main()
* Update multiple scripts to call libregrtest.main()

* Move code into a new _main() function
* Fix loop to cleanup sys.path
* Remove unused import

* add create_file() helper function
* create files using "x" mode instead of "w" to detect when a previous test
  forget to remove a file
* open file for writing in unbuferred mode (buffering=0)
* replace "try/finally: unlink" with self.addCleanup(support.unlink)
* register unlink cleanup function *before* creating new files

* Use context manager on urllib objects to ensure that they are closed on error
* Use self.addCleanup() to cleanup resources even if a test is interrupted
  with CTRL+c