running this command in Terminal.app under your current user
sed -i -e 's/=python /=python3 /g' ~/Library/Arduino15/packages/esp32/hardware/esp32/*/platform.txt
seems to fix it.The command modifies all the platform.txt files under your local installation of the ESP32 tools (~/Library/Arduino15/packages/esp32/hardware/esp32) and replaces the word python by python3 wherever it finds it
(cf Deprecation of Python 2. Solution · Issue #4717 · espressif/arduino-esp32 · GitHub)