old_contents: from lint import Linter
  
  class JavaScript(Linter):
      language = 'javascript'
      cmd = ('jsl', '-stdin')
      regex = r'^\((?P<line>\d+)\):\s+(?P<error>.+)'
  
new_contents: from lint import Linter
  
  class JavaScript(Linter):
      language = 'javascript'
      cmd = ('jsl', '-stdin')
      regex = r'^\((?P<line>\d+)\):\s+(?P<error>.+)'
  
  class EmbeddedJS(JavaScript):
      language = 'html'
      selector = 'source.js.embedded.html'
  
subject: add embedded JS linter