tests: Remove unused imports

tests/mixers/denon_test.py

@@ -1,7 +1,5 @@
-import unittest
-
 from mopidy.mixers.denon import DenonMixer
-from tests.mixers.dummy_test import BaseMixerTest
+from tests.mixers.base_test import BaseMixerTest
 
 class DenonMixerDeviceMock(object):
     def __init__(self):

tests/utils_test.py

@@ -5,7 +5,6 @@ import sys
 import shutil
 import tempfile
 import unittest
-import urllib
 
 from mopidy.utils import *
 from mopidy.models import Track, Artist, Album