[tests] use from .utils import, fixes build with pybuild 3.5

diff --git a/python/tests/test_source_channels.py b/python/tests/test_source_channels.py
index eee696d..74f0acd 100755 (executable)
--- a/python/tests/test_source_channels.py
+++ b/python/tests/test_source_channels.py
@@ -8,7 +8,7 @@ import unittest
 import aubio
 import numpy as np
 from numpy.testing import assert_equal
-from utils import get_tmp_sink_path
+from .utils import get_tmp_sink_path
 
 class aubio_source_test_case(unittest.TestCase):