old_contents: """Test code format and coding standards."""
  import os
  import pep8
  import unittest
  
  
  class TestCodeFormat(unittest.TestCase):
      @staticmethod
      def _get_all_pyfiles():
          pyfiles = []
          for dirpath, _, filenames in os.walk('rewind'):
              pyfiles.extend([os.path.join(dirpath, filename)
                              for filename in filenames
                              if filename.endswith('.py')])
          return pyfiles
  
  
      def testPep8Conformance(self):
          """Test that we conform to PEP8."""
          pep8style = pep8.StyleGuide()
          pyfiles = self._get_all_pyfiles()
          result = pep8style.check_files(pyfiles)
          self.assertEqual(result.total_errors, 0,
                           "Found code syntax errors (and warnings).")
  
new_contents: """Test code format and coding standards."""
  import os
  import pep8
  import unittest
  
  
  class TestCodeFormat(unittest.TestCase):
      @staticmethod
      def _get_all_pyfiles():
          pyfiles = []
          for dirpath, _, filenames in os.walk('rewind'):
              pyfiles.extend([os.path.join(dirpath, filename)
                              for filename in filenames
                              if filename.endswith('.py')])
          return pyfiles
  
      def testPep8Conformance(self):
          """Test that we conform to PEP8."""
          pep8style = pep8.StyleGuide()
          pyfiles = self._get_all_pyfiles()
          result = pep8style.check_files(pyfiles)
          self.assertEqual(result.total_errors, 0,
                           "Found code syntax errors (and warnings).")
  
subject: Fix all E303