Fencing fails in a RHEL 5 or 6 High Availability cluster with a traceback and error "TypeError: can only concatenate list (not 'str') to list"

Issue

• An error occurs when getting the status with fencing agent fence_bladecenter:

2015-02-12 12:11:30 -07:00 Thu node42 [user.info] abrt: detected unhandled Python exception in '/usr/sbin/fence_bladecenter'

• A python exception is thrown when the fencing agent fence_bladecenter tries to get status and abrt catches it:

fencing.py:952:fence_login:TypeError: can only concatenate list (not "str") to list

Traceback (most recent call last):
  File "/usr/sbin/fence_bladecenter", line 143, in <module>
    main()
  File "/usr/sbin/fence_bladecenter", line 126, in main
    conn = fence_login(options, "(username: )")
  File "/usr/share/fence/fencing.py", line 952, in fence_login
    result = conn.log_expect(options, [ "Enter passphrase for key '"+options["-k"]+"':", "Are you sure you want to continue connecting (yes/no)?" ] + options["-c"], int(options["-y"]))
TypeError: can only concatenate list (not "str") to list

• Fencing is failing in my cluster after updating to RHEL 5 Update 11
• Fencing is failing in my cluster after updating to RHEL 6 Update 5
• fence_virt doesn't work, and testing it on the command line gives a traceback and exception