Improve error message when given incorrect module path

Author: TimFelixBeyer

Lib/runpy.py

@@ -135,7 +135,7 @@ def _get_module_details(mod_name, error=ImportError):
         # pkgutil previously raised ImportError
         msg = "Error while finding module specification for {!r} ({}: {})"
         if mod_name.endswith(".py"):
-            msg += (f". Try using '{mod_name[:-3]}' instead of "
+            msg += (f". Try using '{mod_name[:-3].replace('/', '.')}' instead of "
                     f"'{mod_name}' as the module name.")
         raise error(msg.format(mod_name, type(ex).__name__, ex)) from ex
     if spec is None: