code: def debug_bad_encoding(data):
          
          at_fault_files = set()
          for source_file_data in data['source_files']:
              for value in source_file_data.values():
                  try:
                      json.dumps(value)
                  except UnicodeDecodeError:
                      at_fault_files.add(source_file_data['name'])
  
          if at_fault_files:
              log.error('HINT: Following files cannot be decoded properly into '
                        'unicode. Check their content: %s',
                        ', '.join(at_fault_files))
docs: Let's try to help user figure out what is at fault.