This change adds a keyword-only `raise_exceptions` parameter to`multiprocessing.set_forkserver_preload()` that defaults to Falsefor backward compatibility. When set to True, ImportError exceptionsduring module preloading in the forkserver process will be raisedinstead of being silently ignored.This is similar in spirit to the approach attempted inpythonGH-99515,providing developers with the ability to catch import errors duringforkserver module preloading for better debugging and error handling.Changes:- Add _raise_exceptions attribute to ForkServer class- Update set_forkserver_preload() to accept raise_exceptions parameter- Pass raise_exceptions flag through to forkserver main() function- Update main() to conditionally raise ImportError based on flag- Add comprehensive test coverage in test_multiprocessing_forkserver- Update documentation in Doc/library/multiprocessing.rst- Add NEWS entry for Python 3.14

This change adds a keyword-only `raise_exceptions` parameter to`multiprocessing.set_forkserver_preload()` that defaults to Falsefor backward compatibility. When set to True, ImportError exceptionsduring module preloading in the forkserver process will be raisedinstead of being silently ignored.This is similar in spirit to the approach attempted inpythonGH-99515,providing developers with the ability to catch import errors duringforkserver module preloading for better debugging and error handling.Changes:- Add _raise_exceptions attribute to ForkServer class- Update set_forkserver_preload() to accept raise_exceptions parameter- Pass raise_exceptions flag through to forkserver main() function- Update main() to conditionally raise ImportError based on flag- Add comprehensive test coverage in test_multiprocessing_forkserver- Update documentation in Doc/library/multiprocessing.rst- Add NEWS entry for Python 3.14

This change adds a keyword-only `raise_exceptions` parameter to`multiprocessing.set_forkserver_preload()` that defaults to Falsefor backward compatibility. When set to True, ImportError exceptionsduring module preloading in the forkserver process will be raisedinstead of being silently ignored.This is similar in spirit to the approach attempted inpythonGH-99515,providing developers with the ability to catch import errors duringforkserver module preloading for better debugging and error handling.Changes:- Add _raise_exceptions attribute to ForkServer class- Update set_forkserver_preload() to accept raise_exceptions parameter- Pass raise_exceptions flag through to forkserver main() function- Update main() to conditionally raise ImportError based on flag- Add comprehensive test coverage in test_multiprocessing_forkserver- Update documentation in Doc/library/multiprocessing.rst- Add NEWS entry for Python 3.14

This change adds a keyword-only `raise_exceptions` parameter to`multiprocessing.set_forkserver_preload()` that defaults to Falsefor backward compatibility. When set to True, ImportError exceptionsduring module preloading in the forkserver process will be raisedinstead of being silently ignored.This is similar in spirit to the approach attempted inpythonGH-99515,providing developers with the ability to catch import errors duringforkserver module preloading for better debugging and error handling.Changes:- Add _raise_exceptions attribute to ForkServer class- Update set_forkserver_preload() to accept raise_exceptions parameter- Pass raise_exceptions flag through to forkserver main() function- Update main() to conditionally raise ImportError based on flag- Add comprehensive test coverage in test_multiprocessing_forkserver- Update documentation in Doc/library/multiprocessing.rst- Add NEWS entry for Python 3.14

This change adds a keyword-only `raise_exceptions` parameter to`multiprocessing.set_forkserver_preload()` that defaults to Falsefor backward compatibility. When set to True, ImportError exceptionsduring module preloading in the forkserver process will be raisedinstead of being silently ignored.This is similar in spirit to the approach attempted inpythonGH-99515,providing developers with the ability to catch import errors duringforkserver module preloading for better debugging and error handling.Changes:- Add _raise_exceptions attribute to ForkServer class- Update set_forkserver_preload() to accept raise_exceptions parameter- Pass raise_exceptions flag through to forkserver main() function- Update main() to conditionally raise ImportError based on flag- Add comprehensive test coverage in test_multiprocessing_forkserver- Update documentation in Doc/library/multiprocessing.rst- Add NEWS entry for Python 3.14

This change adds a keyword-only `raise_exceptions` parameter to`multiprocessing.set_forkserver_preload()` that defaults to Falsefor backward compatibility. When set to True, ImportError exceptionsduring module preloading in the forkserver process will be raisedinstead of being silently ignored.This is similar in spirit to the approach attempted inpythonGH-99515,providing developers with the ability to catch import errors duringforkserver module preloading for better debugging and error handling.Changes:- Add _raise_exceptions attribute to ForkServer class- Update set_forkserver_preload() to accept raise_exceptions parameter- Pass raise_exceptions flag through to forkserver main() function- Update main() to conditionally raise ImportError based on flag- Add comprehensive test coverage in test_multiprocessing_forkserver- Update documentation in Doc/library/multiprocessing.rst- Add NEWS entry for Python 3.14

This change adds a keyword-only `raise_exceptions` parameter to`multiprocessing.set_forkserver_preload()` that defaults to Falsefor backward compatibility. When set to True, ImportError exceptionsduring module preloading in the forkserver process will be raisedinstead of being silently ignored, causing the forkserver to exitand breaking all use of the forkserver multiprocessing context.This is similar in spirit to the approach attempted inpythonGH-99515,providing developers with the ability to catch import errors duringforkserver module preloading for better debugging and error handling.Implementation:- Add _raise_exceptions attribute to ForkServer class- Update set_forkserver_preload() in both forkserver.py and context.py  to accept raise_exceptions keyword-only parameter- Pass raise_exceptions flag through to forkserver main() function- Update main() to conditionally raise ImportError based on flagTests:- Create new test_multiprocessing_forkserver/test_preload.py with  dedicated tests for raise_exceptions functionality- Remove old test from _test_multiprocessing.py- Add tests for both True/False cases and valid/invalid modules- Ensure proper resource cleanup using try/finallyDocumentation:- Update Doc/library/multiprocessing.rst with detailed description  of raise_exceptions behavior and consequences- Add NEWS entry with contributor attribution- Add Nick Neumann to Misc/ACKSContributed by Nick Neumann.

Add a keyword-only `raise_exceptions` parameter (default False) to`multiprocessing.set_forkserver_preload()`. When True, ImportErrorexceptions during module preloading cause the forkserver to exit,breaking all use of the forkserver multiprocessing context. Thisallows developers to catch import errors during development ratherthan having them silently ignored.Implementation adds the parameter to both the ForkServer class methodand the BaseContext wrapper, passing it through to the forkservermain() function which conditionally raises ImportError instead ofignoring it.Tests are in new test_multiprocessing_forkserver/test_preload.py withproper resource cleanup using try/finally.Documentation describes the behavior, consequences (forkserver exit,EOFError/ConnectionError on subsequent use), and recommends use duringdevelopment.Based on original work by Nick Neumann inpythonGH-99515.Contributed by Nick Neumann.

Add a keyword-only `raise_exceptions` parameter (default False) to`multiprocessing.set_forkserver_preload()`. When True, ImportErrorexceptions during module preloading cause the forkserver to exit,breaking all use of the forkserver multiprocessing context. Thisallows developers to catch import errors during development ratherthan having them silently ignored.Implementation adds the parameter to both the ForkServer class methodand the BaseContext wrapper, passing it through to the forkservermain() function which conditionally raises ImportError instead ofignoring it.Tests are in new test_multiprocessing_forkserver/test_preload.py withproper resource cleanup using try/finally.Documentation describes the behavior, consequences (forkserver exit,EOFError/ConnectionError on subsequent use), and recommends use duringdevelopment.Based on original work by Nick Neumann inpythonGH-99515.Contributed by Nick Neumann.Co-authored-by: Gregory P. Smith <greg@krypto.org>

Add a keyword-only `raise_exceptions` parameter (default False) to`multiprocessing.set_forkserver_preload()`. When True, ImportErrorexceptions during module preloading cause the forkserver to exit,breaking all use of the forkserver multiprocessing context. Thisallows developers to catch import errors during development ratherthan having them silently ignored.Implementation adds the parameter to both the ForkServer class methodand the BaseContext wrapper, passing it through to the forkservermain() function which conditionally raises ImportError instead ofignoring it.Tests are in new test_multiprocessing_forkserver/test_preload.py withproper resource cleanup using try/finally.Documentation describes the behavior, consequences (forkserver exit,EOFError/ConnectionError on subsequent use), and recommends use duringdevelopment.Based on original work by Nick Neumann inpythonGH-99515.Contributed by Nick Neumann.Co-authored-by: Gregory P. Smith <greg@krypto.org>

Add a keyword-only `raise_exceptions` parameter (default False) to`multiprocessing.set_forkserver_preload()`. When True, ImportErrorexceptions during module preloading cause the forkserver to exit,breaking all use of the forkserver multiprocessing context. Thisallows developers to catch import errors during development ratherthan having them silently ignored.Implementation adds the parameter to both the ForkServer class methodand the BaseContext wrapper, passing it through to the forkservermain() function which conditionally raises ImportError instead ofignoring it.Tests are in new test_multiprocessing_forkserver/test_preload.py withproper resource cleanup using try/finally.Documentation describes the behavior, consequences (forkserver exit,EOFError/ConnectionError on subsequent use), and recommends use duringdevelopment.Based on original work by Nick Neumann inpythonGH-99515.Contributed by Nick Neumann.Co-authored-by: Gregory P. Smith <greg@krypto.org>

Add a keyword-only `raise_exceptions` parameter (default False) to`multiprocessing.set_forkserver_preload()`. When True, ImportErrorexceptions during module preloading cause the forkserver to exit,breaking all use of the forkserver multiprocessing context. Thisallows developers to catch import errors during development ratherthan having them silently ignored.Implementation adds the parameter to both the ForkServer class methodand the BaseContext wrapper, passing it through to the forkservermain() function which conditionally raises ImportError instead ofignoring it.Tests are in new test_multiprocessing_forkserver/test_preload.py withproper resource cleanup using try/finally.Documentation describes the behavior, consequences (forkserver exit,EOFError/ConnectionError on subsequent use), and recommends use duringdevelopment.Based on original work by Nick Neumann inpythonGH-99515.Contributed by Nick Neumann.Co-authored-by: aggieNick02 <nick@pcpartpicker.com>Co-authored-by: Claude (Sonnet 4.5) <claude@anthropic.com>Co-authored-by: Gregory P. Smith <greg@krypto.org>

Add a keyword-only `raise_exceptions` parameter (default False) to`multiprocessing.set_forkserver_preload()`. When True, ImportErrorexceptions during module preloading cause the forkserver to exit,breaking all use of the forkserver multiprocessing context. Thisallows developers to catch import errors during development ratherthan having them silently ignored.Implementation adds the parameter to both the ForkServer class methodand the BaseContext wrapper, passing it through to the forkservermain() function which conditionally raises ImportError instead ofignoring it.Tests are in new test_multiprocessing_forkserver/test_preload.py withproper resource cleanup using try/finally.Documentation describes the behavior, consequences (forkserver exit,EOFError/ConnectionError on subsequent use), and recommends use duringdevelopment.Based on original work by Nick Neumann inpythonGH-99515.Contributed by Nick Neumann.Co-authored-by: aggieNick02 <nick@pcpartpicker.com>Co-authored-by: Claude (Sonnet 4.5) <noreply@anthropic.com>Co-authored-by: Gregory P. Smith <greg@krypto.org>

…er_preload` (GH-141859)Add a keyword-only `on_error` parameter to `multiprocessing.set_forkserver_preload()`. This allows the user to have exceptions during optional `forkserver` start method module preloading cause the forkserver subprocess to warn (generally to stderr) or exit with an error (preventing use of the forkserver) instead of being silently ignored.This _also_ fixes an oversight, errors when preloading a `__main__` module are now treated the similarly. Those would always raise unlike other modules in preload, but that had gone unnoticed as up until bug fix PRGH-135295 in 3.14.1 and 3.13.8, the `__main__` module was never actually preloaded.Based on original work by Nick Neumann@aggieNick02 inGH-99515.