go work vendor
stderr 'go: no dependencies to vendor'
! exists vendor/modules.txt
! go list .
stderr 'go: no modules were found in the current workspace'
mkdir vendor
mv bad_modules.txt vendor/modules.txt
! go list .
stderr 'go: no modules were found in the current workspace'

-- bad_modules.txt --
# a/module
a/package
-- go.work --
go 1.21