[pkg] improve error message for module detection on saving pass (pyto…

…rch#73106)

Summary:
Pull Request resolved: pytorch#73106

The original error message didn't have next steps, and someone got confused. This error message should make debugging a bit easier.

Test Plan: Imported from OSS

Reviewed By: ngimel

Differential Revision: D34559499

Pulled By: PaliC

fbshipit-source-id: fd5fec9c4db10a20775435a587bad24336a671ef
(cherry picked from commit efdcf1e)

torch/package/package_exporter.py

@@ -607,7 +607,8 @@ def _check_mocked_error(module: Optional[str], field: Optional[str]):
                             f"Object '{field}' from module {module} was mocked out during packaging "
                             f"but is being used in resource - {resource} in package {package}. "
                             "If this error is happening during 'save_pickle', please ensure that your "
-                            "pickled object doesn't contain any mocked objects."
+                            "pickled object doesn't contain any mocked objects. Try interning or externing"
+                            f"{module} if {field} is supposed to be in the package."
                         )
                     else:
                         return