test_unraisable() of test_exceptions expects that PyErr_WriteUnraisable(method)
fails on repr(method).
Before the previous change (7b8df4a5d81d), slot_tp_finalize() called
PyErr_WriteUnraisable() with a PyMethodObject. In this case, repr(method) calls
repr(self) which is BrokenRepr.__repr__() and the calls raises a new exception.
After the previous change, slot_tp_finalize() uses an unbound method: repr() is
called on a regular __del__() method which doesn't call repr(self). repr()
doesn't fail anymore.
PyErr_WriteUnraisable() doesn't call __repr__() anymore, so remove BrokenRepr
unit test.
This restores details lost in revision 097f4fda61a4 (since Python 3.3,
related to the new OSError subclasses). Further additions:
* Markup for attributes and constructor signature
* Explain "winerror" and "filename2"
* Extend test to check for filename2 defaulting to None
* Clarify that the constructor can return a subclass
I have intentionally left out any details of allowing more than five
arguments, or how the "args" attribute is set for four or more arguments.
These details seem to be dependent on the Python version and platform.
now register both filenames in the exception on failure.
This required adding new C API functions allowing OSError exceptions
to reference two filenames instead of one.
