ID 376451 - Attempting to use a Custom Viewer Process as a LUT when rendering a Flipbook throws exception.

Problem summary
Users are experiencing problems using Custom LUT Viewer Processes on Flipbooks.

As displayed below, if the user attempts to burn-in their custom LUT ( In the example's case named "myLUT" )on Flipbook Render, the Flipbook fails with the following:
​

​

This stops users from reviewing Flipbooks with custom LUTS.

Customer reported version
nuke.11.2v1

Customer reported platform
n_a_linux

Steps to reproduce

1) Copy the attached Gizmo into your ~/.nuke directory

2) Add this line in your ~/.nuke/init.py file and save it: 

nuke.ViewerProcess.register("myLUT", nuke.Node, ("myLUT", ""))

3) Open Nuke, create a ColorWheel node

4) Select the ColorWheel node and from the top toolbar, navigate to "Render -> Flipbook Selected".

5) Within the 'LUT' field, select 'myLUT' and check the 'Burn in the LUT' option:

 ​

​

6) Render the Flipbook by pressing 'OK'.

Result: The render will fail and throw the exception displayed above.

Workaround
Unknown.

Reproduced by support

This bug has been reproduced in:
Nuke11.3v1- Windows 7 - Mac10.13 - CentOS7
Nuke11.2v1 - Windows 7
Nuke11.1v1 - Windows 7
Nuke11.0v1 - Windows 7
Nuke10.5v1 - Windows 7
Nuke10.0v1 - Windows 7- Mac10.13 - CentOS7 - regression


Unable to reproduce the bug in:
Nuke9.0v9 - Windows 7 - Mac10.13 - CentOS7

Earliest version tested
- This issue no longer appears in this version and has regressed

Expected behaviour
Flipbooks should be able to use Custom Viewer Processes as LUTS

Actual behaviour
Attempting to render a Flipbook with a Custom Viewer Process throws exceptions.