Tensorflow cannon import name 'gradients_util'
You must use version of benchmark compatible with your TensorFlow version.
Determine it using pip show tensorflow.
Then go to cloned repository of benchmarks, and checkout to required branch, for example git checkout cnn_tf_v1.13_compatible.
Previous comments suggested to use TensorFlow 2.0, but I don't think author of question needs it, as long as it's still unreleased and has a lot of API-breaking changes.
P. S. You should've say that you are trying to launch benchmarks from tensorflow/benchmarks in your question.
After doing  

pip install tensorflow-gpu 

I am trying to 

import gradients_util from tensorflow.python.ops  

but I get 

cannot import name 'gradients_util'  

error. How can I fix this?