exceptions when saving oleans are not user-visible

Prerequisites

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  • Checked that your issue isn't already filed.
    • Specifically, check out the wishlist, open RFCs,
      or feature requests.
  • Reduced the issue to a self-contained, reproducible test case.

Description

The olean compilation process emits user-friendly messages for several failure scenarios, such as https://github.com/leanprover-community/lean/blob/v3.45.0/src/library/module_mgr.cpp#L128. However, the failure is not notified to the user. This includes heartbeat exception reporting, as in #749.

Steps to Reproduce

1. Create an empty olean and remove write permissions
2. Use lean --make to compile something that would overwrite the above file

Expected behavior: Non-zero exit code and a message

Actual behavior: No reported error

Reproduces how often: 100%

Versions

Lean (version 3.45.0, commit 22b09be35ef6, Release)

Start with the olean failure handling in src/library/module_mgr.cpp at the linked location, then reproduce the issue by making an olean unwritable and running lean --make. Done means the failure, including heartbeat exceptions, produces a user-visible message and a non-zero exit code.