Merge pull request #1044 from jcstr/patch1

Remove unused imports

Author: lukpueh

tests/test_slow_retrieval_attack.py

@@ -45,15 +45,12 @@
 from __future__ import unicode_literals
 
 import os
-import sys
 import tempfile
 import random
 import time
 import shutil
-import json
 import subprocess
 import logging
-import sys
 import unittest
 
 import tuf.log