Investigate errors from "src/libcore/result.rs:906"

[pdehaan]

via the magnificent @rpappalax:

panicked at 'called `Result::unwrap()` on an `Err` value 
"No such file or directory"
/checkout/src/libcore/result.rs:906:4

"result.rs" sounds like maybe Rust? Not sure if we need full Firefox source, versus just the bits and pieces we're currently extracting from the ZIP file. But now armed with a starter error message above, it should hopefully be easier to Google and track down possible causes/solutions.

[rpappalax]

can't repro