OpenGL errors rendering transparency on mesa

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I get something similar; I can confirm that I only get the following error output if I enable transparency - if both actors are fully opaque then Mesa doesn’t report any errors:

$ MESA_DEBUG=1 python main.py
Mesa: User error: GL_INVALID_VALUE in glTexImage2D(internalFormat=GL_NONE)
Mesa: 1 similar GL_INVALID_VALUE errors
Mesa: User error: GL_INVALID_FRAMEBUFFER_OPERATION in glClear(incomplete framebuffer)
Mesa: User error: GL_INVALID_FRAMEBUFFER_OPERATION in glBlitFramebuffer(incomplete draw/read buffers)
Mesa: User error: GL_INVALID_FRAMEBUFFER_OPERATION in glDrawRangeElements(incomplete framebuffer)
Mesa: User error: GL_INVALID_FRAMEBUFFER_OPERATION in glClear(incomplete framebuffer)
Mesa: User error: GL_INVALID_FRAMEBUFFER_OPERATION in glBlitFramebuffer(incomplete draw/read buffers)
Mesa: User error: GL_INVALID_FRAMEBUFFER_OPERATION in glDrawRangeElements(incomplete framebuffer)