pyhon-can driver broken due to upstream changes

[oystub]

The flush_tx_buffer() method in python-can now raises a NotImplementedError for many interface types like socketcan. This breaks sending messages on systems where python-can is installed. I raised an upstream issue for python-can requesting a change in this behaviour here: hardbyte/python-can#1922

In the meantime (or if they decide to keep this behaviour in python-can), a suggested workaround can be found in #78