Experimenting with more structured ways to handle command-line input/output in Rust

Add basic error handling for invalid paths in proc_macro attribute

Makes it much clearer what the problem is, and where to find the invalid path

Created by  finchie  on July 3, 2024
V5S5K33ALIEG5ZABUSAPO4ULHEBFDB2PLTW27A4BFS342SJG7URQC
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