The previous fix only handled the case of the parent package of __main__
failing to initialize.
Also make the "Error while finding spec" formatting slightly more appealing,
and document and test that the module name must be absolute.
Initialize package before calling find_spec() for __main__, so that we do not
incorrectly handle exceptions from __init__.py. When runpy is used from the
Python CLI, use an internal exception rather than ImportError, to avoid
catching unexpected exceptions.
Also remove exception message rewriting in _run_module_as_main(), because it
seems to be redundant with the _get_main_module_details() function.
I have compared output between pre- and post-patch runs of these tests
to make sure there's nothing missing and nothing broken, on both
Windows and Linux. The only differences I found were actually tests
that were previously *not* run.
The concept of .pyo files no longer exists. Now .pyc files have an
optional `opt-` tag which specifies if any extra optimizations beyond
the peepholer were applied.
Note that __spec__.name is not currently guaranteed to be in
sys.modules when the code is running, only __name__ is.
The "running module is in sys.modules" invariant will be
expanded to also cover __spec__.name in a subsequent patch.
