Apologies if any of this is incorrect, or if this has already been reported. This is my first bug report.

System Information
Mac Pro
2.93 GHz Quad-Core Intel Xeon
18GB 1066 MHz DDR3 ECC
NVIDIA GeForce GTX 660 2048 MB

Blender Version
Broken: 2.77a abf6f08

Short description of error
After enabling the nodewrangler add-on I proceed to build a shader network. IE: A simple diffuse and glossy input into a mix shader then connected to the output node. When using the 'Shift+s' to switch the mix node to an add node I get the following error:

Traceback (most recent call last):
  File "/Applications/Blender/blender.app/Contents/Resources/2.77/scripts/addons/node_wrangler.py", line 1897, in execute
    force_update(context)
NameError: name 'force_update' is not defined

location: <unknown location>:-1

Exact steps for others to reproduce the error
The same error can be generated whenever I try to use the 'Shift+S' to swap out one node for another.

Thanks,
Brandon Hix