py library deprecated

[shinglerb]

The py library has been in maintenance only mode for a while and recommend using pathlib.
Perhaps pathlib.os.path and pathlib.os.defpath could be used instead?

.//src/devpi_tokens/client.py:177:            path = py.path.local(args.file)
.//src/devpi_tokens/tests/test_functional.py:126:    path = py.path.local.sysfind("devpi-server")
.//src/devpi_tokens/tests/test_functional.py:127:    init_path = py.path.local.sysfind("devpi-init")