code: def flake(self, message):
          
          err_range = {
              'start': {'line': message.lineno - 1, 'character': message.col},
              'end': {'line': message.lineno - 1, 'character': len(self.lines[message.lineno - 1])},
          }
  
          severity = lsp.DiagnosticSeverity.Warning
          for message_type in PYFLAKES_ERROR_MESSAGES:
              if isinstance(message, message_type):
                  severity = lsp.DiagnosticSeverity.Error
                  break
  
          self.diagnostics.append({
              'source': 'pyflakes',
              'range': err_range,
              'message': message.message % message.message_args,
              'severity': severity
          })
docs: Get message like <filename>:<lineno>: <msg>