threading.Thread.isAlive() has been removed in python3.9. The following worker package script, src/Pegasus/tools/worker_utils.py, uses this method. Tools like pegasus-transfer will break if run on a node with python 3.9+. To fix this, usage of that method needs to be changed to is_alive(), which works in python2.7+.

References:

• https://github.com/python/cpython/pull/15225
• https://bugs.python.org/issue37804
• https://docs.python.org/2.7/library/threading.html