* Try to match the module name pattern with module names constructed
starting from different parent directories of the filename.
E.g., for "/path/to/package/module" try to match with
"path.to.package.module", "to.package.module", "package.module" and
"module".
* Ignore trailing "/__init__.py".
* Ignore trailing ".pyw" on Windows.
* Keep matching with the full filename (without optional ".py" extension)
for compatibility.
* Only ignore the case of the ".py" extension on Windows.
Add tests for "import", pkgutil.resolve_name() and unittest.mock.path()
for cases when "import a.b as x" and "from a import b as x" give
different results.
* bpo-39336: Allow setattr to fail on modules which aren't assignable
When attaching a child module to a package if the object in sys.modules raises an AttributeError (e.g. because it is immutable) it causes the whole import to fail. This now allows immutable packages to exist and an ImportWarning is reported and the AttributeError exception is ignored.
