[bigfooted]

Proposed Changes

The "FATAL: ThreadSanitizer: unexpected memory mapping" message comes from the TSan runtime. It happens when the kernel's ASLR randomization is too high for TSan's fixed shadow-memory layout (vm.mmap_rnd_bits=32). That is the default on recent GitHub runner images and kernels.
The failing step is the bootstrap of ninja, because the Cantera subproject builds its own ninja when none is on the PATH. The TSan flags from the job are inherited by that bootstrap. The freshly built ./ninja is therefore TSan-instrumented and dies on startup with exit status 66, which gives the Python traceback you see.

Related Work

Resolve any issues (bug fix or feature request), note any related PRs, or mention interactions with the work of others, if any.

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