update-tests-metadata failing - No such file or directory @ rb_sysopen - knapsack/rspec*_pg9_*.json (Errno::ENOENT)

Job #308189840 failed for 969d098e:

$ update_tests_metadata
scripts/merge-reports:16:in `read': No such file or directory @ rb_sysopen - knapsack/rspec*_pg9_*.json (Errno::ENOENT)
	from scripts/merge-reports:16:in `block in <main>'
	from scripts/merge-reports:15:in `each'
	from scripts/merge-reports:15:in `<main>'
Loading knapsack/report-master.json...