In what sense is this being flagged as easy? All the runpy code knows at
this point is that it asked the import system for the __main__ module's
code object and didn't get one. __main__ always exists, so the module is
definitely able to be found - working out after the fact why the code
object can't be provided isn't the simplest thing in the world. For
example, "./python -m sys" triggers a similar error message.

Or are you merely suggesting the addition of something like "(e.g.
directory or zipfile does not contain __main__.py)" to the current error
message when the requested module is "__main__"?