It might be better to show original error message as well

[k-yomo]

We've got an error at the following point even though it's definitely json file... Eventually we realized it was caused by encoding issue. So It would be better to show original error message as well to let us know what is the actual reason for getting config error.

begin
    JSON.parse(File.read(task['schema_file']))
rescue => e
    raise ConfigError.new "schema_file #{task['schema_file']} is not a JSON file"
end

i would be happy to implement this.