FileNotFoundException Not Very Explicit

[zhuchcn]

pipeline-Nextflow-config/config/schema/schema.config

Line 63 in f3448ac

throw new FileNotFoundException("${file} does not exist.")

I found this error can be unclear sometimes. In my case, one of the files was given as an empty string. So All it prints out is:

ERROR ~ Unable to parse config file: 'metapipeline-DNA/module/recalibrate_BAM/./default.config'

   does not exist.

I had other cases that I had to spend a lot of time figuring out where the error came from. Maybe we can also print out what variable the path is missing.

[yashpatel6]

Agreed, it should be better, it'd need a slight update to the error handling to make sure the error message has the necessary information without having to pass it all to all of the functions