Exception if enable "Network Renderer" before "V-Ray for Blender"

[ghost]

On User Preferences, enabling "V-Ray for Blender" fails with an exception if you try it after enabling "Network Renderer". But if you restart, enable "V-Ray for Blender" first, and then enable "Network Renderer", both options work. The stack trace is

Exception in module register(): '/usr/ChaosGroup/Blender 2.78 (With V-Ray Additions)/2.78/scripts/addons/vb30/init.py' Traceback (most recent call last): File "/usr/ChaosGroup/Blender 2.78 (With V-Ray Additions)/2.78/scripts/modules/addon_utils.py", line 349, in enable mod.register() File "/usr/ChaosGroup/Blender 2.78 (With V-Ray Additions)/2.78/scripts/addons/vb30/init.py", line 53, in register plugins.register() File "/usr/ChaosGroup/Blender 2.78 (With V-Ray Additions)/2.78/scripts/addons/vb30/plugins/init.py", line 894, in register bpy.utils.register_class(regClass) ValueError: register_class(...): already registered as a subclass

[ghost]

Exceptions were with installer vrayblender35-2.78-86e73c2-x86_64-centos7.2.1511.tar.bz2 on Ubuntu 16.04. I tried installing on another machine, and was able to enable "Network Renderer" then "V-Ray for Blender", but I then disable "V-Ray for Blender", I get an error with this stack trace:

`Traceback (most recent call last): File "/usr/ChaosGroup/Blender 2.78 (With V-Ray Additions)/2.78/scripts/modules/addon_utils.py", line 349, in enable mod.register() File "/usr/ChaosGroup/Blender 2.78 (With V-Ray Additions)/2.78/scripts/addons/vb30/init.py", line 53, in register plugins.register() File "/usr/ChaosGroup/Blender 2.78 (With V-Ray Additions)/2.78/scripts/addons/vb30/plugins/init.py", line 894, in register bpy.utils.register_class(regClass) ValueError: bpy_struct "VRayCamera" registration error: CameraStereoscopic could not register

`

[poseidon4o]

@k1643 I tested that scenario on Ubuntu 16 and could not reproduce it, except when unloading the V-Ray addon. Currently unloading our addon does not work correctly and requires blender restart.