mmap failure in tests/scripts/check_deriv.py

[ye-luo]

Describe the bug
It seems that it choked Permutter
#4937 (comment)

@Paul-St-Young is mmap really needed?

[prckent]

I wonder if this is the root cause? Are other mmaps done successfully in other test scripts?

[ye-luo]

I wonder if this is the root cause? Are other mmaps done successfully in other test scripts?

The two failing tests both include a line of mmap.

[Paul-St-Young]

@ye-luo mmap is not strictly necessary. It just has some nice utilities for text parsing.
It would be totally fine to rewrite the script to parse ascii text.