Travis with WITH_CMAKE=true, WITH_CUDA=true still has the CPU_ONLY=ON flag set, so it never builds the cuda code with cmake.
See https://github.com/BVLC/caffe/blob/master/scripts/travis/travis_build_and_test.sh line 10. Is there a reason for this or just oversight?