Issue #14938: importlib.abc.SourceLoader.is_package() now takes the

Issue #14938: importlib.abc.SourceLoader.is_package() now takes the
module name into consideration when determining whether a module is a
package or not. This prevents importing a module's __init__ module
directly and having it considered a package, which can lead to
duplicate sub-modules.

Thanks to Ronan Lamy for reporting the bug.