py311-exceptiongroup

Backport of PEP 654 (exception groups)

This is a backport of the BaseExceptionGroup and ExceptionGroup classes from Python 3.11. It contains the following: - The exceptiongroup.BaseExceptionGroup and exceptiongroup.ExceptionGroup classes - A utility function (exceptiongroup.catch()) for catching exceptions possibly nested in an exception group - Patches to the TracebackException class that properly formats exception groups (installed on import) - An exception hook that handles formatting of exception groups through TracebackException (installed on import) If this package is imported on Python 3.11 or later, the built-in implementations of the exception group classes are used instead, TracebackException is not monkey patched and the exception hook won't be installed.