Smoke test: pin libtmux to tmux-python/libtmux#672#1043

tony wants to merge 3 commits into

mastertmux-python/tmuxp:masterfrom

chore/test-libtmux-0.57-paritytmux-python/tmuxp:chore/test-libtmux-0.57-parityCopy head branch name to clipboard