Make update-flaky-tests to work again and support all bots

Tools/Scripts/webkitpy/layout_tests/models/test_expectations.py

 # Copyright (C) 2010 Google Inc. All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 # notice, this list of conditions and the following disclaimer.
 #     * Redistributions in binary form must reproduce the above
 # copyright notice, this list of conditions and the following disclaimer
@@ skipping 384 matching lines @@
             and self.parsed_specifiers == other.parsed_specifiers
             and self.matching_configurations == other.matching_configurations
             and self.expectations == other.expectations
             and self.parsed_expectations == other.parsed_expectations
             and self.comment == other.comment
             and self.matching_tests == other.matching_tests
             and self.warnings == other.warnings
             and self.is_skipped_outside_expectations_file == other.is_skipped_outside_expectations_file)
 
     def is_invalid(self):
-        return self.warnings and self.warnings != [TestExpectationParser.MISSING_BUG_WARNING]
+        return bool(self.warnings and self.warnings != [TestExpectationParser.MISSING_BUG_WARNING])
 
     def is_flaky(self):
         return len(self.parsed_expectations) > 1
 
     def is_whitespace_or_comment(self):
         return bool(re.match("^\s*$", self.original_string.split('#')[0]))
 
     @staticmethod
     def create_passing_expectation(test):
         expectation_line = TestExpectationLine()
@@ skipping 687 matching lines @@
             # If reconstitute_only_these is an empty list, we want to return original_string.
             # So we need to compare reconstitute_only_these to None, not just check if it's falsey.
             if reconstitute_only_these is None or expectation_line in reconstitute_only_these:
                 return expectation_line.to_string(test_configuration_converter)
             return expectation_line.original_string
 
         def nones_out(expectation_line):
             return expectation_line is not None
 
         return "\n".join(filter(nones_out, map(serialize, expectation_lines)))