Thank you! I switched back to the i2c_bus module and the code you provided and it worked. No more errors.
All that was missing was converting the struct to a short:
def get_moisture():
i2c = i2c_bus.easyI2C(i2c_bus.PORTA, 0x36)
i2c.write_u8(0x0f, 0x10)
wait_ms(5)
val = i2c.read(2)
val = ustruct.unpack(">H", val)[0]
return val