Was getting errors "Serial" and "MSBFIRST" not defined in this scope.
Fixed by adding #include <Arduino.h> to library file MPU9250.h
look for it in .pio/libdeps/esp32dev/SparkFun MPU-9250 9 DOF IMU Breakout / src/ 
~~~~~~~~~~~~
Fix for compiler not finding SPI.h or Wire.h
Put it into platformio.init
lib_deps = 
	sparkfun/SparkFun MPU-9250 9 DOF IMU Breakout@^1.0.2
	adafruit/Adafruit NeoPixel@^1.10.7
	SPI
	Wire
~~~~~~~~~~~~~