message: Changed a comparison with an integer to use ==
  Correct a syntax error on Python 3.8
  ```
  /mesh/support/config.py:135: SyntaxWarning: "is" with a literal. Did you
  mean "=="?
  if len(path) is 0:
  ```
diff: @@ -132,7 +132,7 @@ class ConfigBuilder:
  env = self.env
  path = run_cmd('which %s' % (program))
  - if len(path) is 0:
  + if len(path) == 0:
  stderr.write('required program "%s" not found.\n' % program)
  exit(1)
  