AttributeError: 'CalledProcessError' object has no attribute 'stdout'

[mithro]

tansell@tansell-z620-l2:~/foss/timvideos/hdmi2usb/lite/opsis-soc$ opsis-mode-switch --mode=serial
WARNING:root:unbind-helper not found, will have to run as root!
Using FX2 firmware /usr/local/google/home/tansell/foss/timvideos/hdmi2usb/lite/HDMI2USB-mode-switch/hdmi2usb/firmware/fx2/opsis/usb-uart.ihx
Traceback (most recent call last):
  File "/usr/local/google/home/tansell/foss/timvideos/hdmi2usb/lite/HDMI2USB-mode-switch/hdmi2usb/modeswitch/boards.py", line 126, in load_fx2
    output = subprocess.check_output(cmdline, stderr=subprocess.STDOUT)
  File "/usr/local/google/home/tansell/foss/timvideos/hdmi2usb/lite/conda/lib/python3.4/subprocess.py", line 620, in check_output
    raise CalledProcessError(retcode, process.args, output=output)
subprocess.CalledProcessError: Command '['fxload', '-t', 'fx2lp', '-D', '/dev/bus/usb/003/006', '-I', '/usr/local/google/home/tansell/foss/timvideos/hdmi2usb/lite/HDMI2USB-mode-switch/hdmi2usb/firmware/fx2/opsis/usb-uart.ihx']' returned non-zero exit status 255

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/local/google/home/tansell/foss/timvideos/hdmi2usb/lite/conda/bin/opsis-mode-switch", line 9, in <module>
    load_entry_point('hdmi2usb.modeswitch', 'console_scripts', 'opsis-mode-switch')()
  File "/usr/local/google/home/tansell/foss/timvideos/hdmi2usb/lite/HDMI2USB-mode-switch/hdmi2usb/modeswitch/cli.py", line 218, in main
    verbose=args.verbose)
  File "/usr/local/google/home/tansell/foss/timvideos/hdmi2usb/lite/HDMI2USB-mode-switch/hdmi2usb/modeswitch/boards.py", line 128, in load_fx2
    if b"can't modify CPUCS: Protocol error\n" not in e.stdout:
AttributeError: 'CalledProcessError' object has no attribute 'stdout'