In stm32w_flasher replaced hal-* calls with usage of pyudev.
In stm32w_flasher added check for pyudev and updated ubuntu package instructions.
In stm32w_flasher adapted error message for missing pyudev.
Merge pull request #386 from chrta/stm32w_flasher_udev

In stm32w_flasher replaced hal-* calls with usage of pyudev.