util: Flatten cython tests layout

ref:7427208d08ebeb9e88247fb7dac6445bc814d756

util/tests/cython/test_generic.py → util/generic/ut_cython/test_generic.py

@@ -10,7 +10,6 @@ from util.generic.maybe_ut import TestMaybe
 from util.generic.ptr_ut import TestHolder
 from util.generic.string_ut import TestStroka
 from util.generic.vector_ut import TestVector
-from util.string.cast_ut import TestFromString, TestToString
 
 # Test discovery does not work in cython modules.
 # Reexporting test classes here to satisfy pylint and pytest.
@@ -24,6 +23,4 @@ __all__ = [
     'TestMaybe',
     'TestStroka',
     'TestVector',
-    'TestFromString',
-    'TestToString',
 ]

util/string/ut_cython/test_string.py

@@ -0,0 +1,13 @@
+# -*- coding: utf-8 -*-
+
+from __future__ import print_function, absolute_import, division
+
+from util.string.cast_ut import TestFromString, TestToString
+
+# Test discovery does not work in cython modules.
+# Reexporting test classes here to satisfy pylint and pytest.
+
+__all__ = [
+    'TestFromString',
+    'TestToString',
+]