In the situation where PTL is running on a mom host, changes that need PBS admin privileges, such as setting a node attribute, will cause PTL to ssh to the server node. If there is a warning from ssh the message list from PbsManagerError will not be what a PTL test expected.
For example if the message list was:
e.msg = ['<ssh warning message>', 'qmgr obj=<server> svr=default: Invalid request', 'qmgr: Error (15004) returned from server']
then a test expecting e.msg to have "Invalid request" will fail.