Use is_alive in favour of isAlive for Python 3.9 compatibility. (#2940)
Use is_alive in favour of isAlive for Python 3.9 compatibility. (#2940)


spotify/luigi,dlstadther/luigi,dlstadther/luigi,dlstadther/luigi,jamesmcm/luigi,riga/luigi,jamesmcm/luigi,dlstadther/luigi,jamesmcm/luigi,riga/luigi,spotify/luigi,riga/luigi,jamesmcm/luigi,riga/luigi,spotify/luigi,spotify/luigi