Warning "USD arnold attribute b not recognized"

[sebastienblor]

When rendering some scenes (for example test_0212), we see warnings saying

00:00:00   173MB WARNING | USD arnold attribute b not recognized in user_data_rgb for /materials/arnold_materialbuilder5/user_data_rgb1
00:00:00   173MB WARNING | USD arnold attribute g not recognized in user_data_rgb for /materials/arnold_materialbuilder5/user_data_rgb1
00:00:00   173MB WARNING | USD arnold attribute r not recognized in user_data_rgb for /materials/arnold_materialbuilder5/user_data_rgb1
00:00:00   173MB WARNING | USD arnold attribute rgb not recognized in user_data_rgb for /materials/arnold_materialbuilder5/user_data_rgb1

This shows up quite frequently, always related to user_data_rgb, so there must be something wrong in the translator

[autodesk-oss-arnold-bot[bot]]

Issue synced internally to ARNOLD-13305