Building/Compiling MicroPython with Pybytes
Rather than answering a dead post I thought I would start fresh.
When building MicroPython from the Dev branch Pybytes is not enabled by default. To compile MicroPython with Pybytes as a builtin library you need to specify the VARIANT in the make command;
make BOARD=FIPY ESPPORT=/dev/ttyACM0 VARIANT=PYBYTES flash
I couldn't find this documented anywhere so thought it would be worth posting up.