gen-default-modes.py warning with python 3.8

When building mutter on Arch Linux with python 3.8, I see the below warning:

[131/620] Generating meta-default-modes with a custom command.
/home/glitsj16/mutter-performance/src/mutter-performance/src/backends/native/gen-default-modes.py:65: SyntaxWarning: "is" with a literal. Did you mean "=="?
  flags += "NHSYNC" if hsync[0] is '-' else "PHSYNC"
/home/glitsj16/mutter-performance/src/mutter-performance/src/backends/native/gen-default-modes.py:67: SyntaxWarning: "is" with a literal. Did you mean "=="?
  flags += "NVSYNC" if vsync[0] is '-' else "PVSYNC"

Nothing breaks, but I wanted to file a FYI issue here nonetheless.