bpo-30843: regrtest fixes sys.path, restore test.bisect (#2567)

* Rename again Lib/test/bisectcmd.py to Lib/test/bisect.py
* regrtest now removes '' and Lib/test/ from sys.path
* Use absolute import in test_bisect
diff --git a/Lib/test/test_bisect.py b/Lib/test/test_bisect.py
index 5c3330b..9bed28e 100644
--- a/Lib/test/test_bisect.py
+++ b/Lib/test/test_bisect.py
@@ -1,3 +1,4 @@
+from __future__ import absolute_import
 import sys
 import unittest
 from test import test_support