tests: test_pipe.py. Fix missing import.

* Fix missing import (does not impact 'make test', fixes issue
  running under 'make test-shell')

Change-Id: I634378a8809df5c5b9671555932e797d04a2abbb
Signed-off-by: Paul Vinciguerra <pvinci@vinciconsulting.com>
diff --git a/test/test_pipe.py b/test/test_pipe.py
index 2d3c1ec..6a0b4a0 100644
--- a/test/test_pipe.py
+++ b/test/test_pipe.py
@@ -1,14 +1,15 @@
 #!/usr/bin/env python
 from socket import AF_INET, AF_INET6, inet_pton
-
-from framework import VppTestCase, VppTestRunner
-from vpp_interface import VppInterface
-from vpp_ip_route import VppIpTable, VppIpRoute, VppRoutePath
+import unittest
 
 from scapy.packet import Raw
 from scapy.layers.l2 import Ether
 from scapy.layers.inet import IP, UDP
 
+from framework import VppTestCase, VppTestRunner
+from vpp_interface import VppInterface
+from vpp_ip_route import VppIpTable, VppIpRoute, VppRoutePath
+
 
 class VppPipe(VppInterface):
     """