Install module "pyserial" instead of "serial"

[damien-robotsix]

I was trying to flash a Pixhawk v6x though the docker and even with appropriate rights, the upload python script was failing to connect to the board.

Digging a bit I got a reason: module 'serial' has no attribute 'Serial'

This is due to the fact that the module 'serial' is installed in the docker and not 'pyserial'.

Is this wanted? do we need the module 'serial' or is it a typo mistake?

Anyway, without the module pyserial, the upload script won't work.

Thank you for your feedback.

[damien-robotsix]

A consequence is that the module future is not installed anymore (it was a dependency of serial) so I had to put it back in the pip module list to be installed as the module 'future' is required to build the firmware.

Again, this assume that the module 'serial' itself is not needed but this I am unsure. (I never needed it in my usage of the PX4 firmware and better not have it since it might conflict with pyserial).