def lint_file_paths(files, ext)
        file_list = files.map { |f| f[:filename] }.compact
        # Lints accept files differently
        ext == :ruby ? file_list.join(' ') : file_list.join(',')
      end
def lint_file_paths(files, ext)
        file_list = files.map { |f| f[:filename] }.compact
        # Lints accept files differently
        ext == :ruby ? file_list.join(' ') : file_list.join(',')
      end
Get list of file paths
 @param files [Hash] hash of files denoted by key 'filename'
 @param ext [String] file extension - different extensions are joined different ways
 @return [String] file paths delimited by comma or space