* Add three new bytecodes: LIST_TO_TUPLE, LIST_EXTEND, SET_UPDATE. Use them to implement star unpacking expressions.

* Remove four bytecodes BUILD_LIST_UNPACK, BUILD_TUPLE_UNPACK, BUILD_SET_UNPACK and  BUILD_TUPLE_UNPACK_WITH_CALL opcodes as they are now unused.

* Update magic number and dis.rst for new bytecodes.

…em (#18006)

* 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.