v5.9-RC3 SkyBoxBackground rendering with OSMesa gives errors

I use the following code:

tex1 = CreateTexture('model.hdr')
renderView1.BackgroundTexture = tex1
renderView1.UseSkyboxBackground = 1

using Mesa 18.3.3 in batch mode,I get the following errors, although the image gets saved correctly

(  76.256s) [pvbatch         ]vtkOpenGLFramebufferObj:456    ERR| vtkOpenGLFramebufferObject (0x225506f0): Frame buffer object was not initialized correctly.
Current framebuffer is bind to framebuffer object 8
color attachment 0:
 this attachment is a texture with name: 19
 its mipmap level is: 0
 this is a cube map texture and the image is contained in face 34069
 this is a 3D texture and the zoffset of the attached image is 34069
color attachment 1:
 this attachment is a texture with name: 19
 its mipmap level is: 0
 this is a cube map texture and the image is contained in face 34070
 this is a 3D texture and the zoffset of the attached image is 34070
color attachment 2:
 this attachment is a texture with name: 19
(  76.256s) [pvbatch         ]vtkOpenGLFramebufferObj:1376   ERR| vtkOpenGLFramebufferObject (0x225506f0): The framebuffer is incomplete : FRAMEBUFFER_INCOMPLETE_ATTACHMENT
 its mipmap level is: 0