Merge pull request #1656 from minrk/embed_kernel_tests

ensure kernels are cleaned up in embed_kernel tests

use contextmanager to ensure kernel manager sockets are closed at the end of tests, preventing delayed 'could not close sockets' errors in later tests.

closes  #1653

IPython/zmq/tests/test_embed_kernel.py

@@ -17,6 +17,7 b' import sys'
 import tempfile
 import time
 
+from contextlib import contextmanager
 from subprocess import Popen, PIPE
 
 import nose.tools as nt
@@ -51,12 +52,13 b' def teardown():'
         pass
 
 
-def _launch_kernel(cmd):
+@contextmanager
+def setup_kernel(cmd):
     """start an embedded kernel in a subprocess, and wait for it to be ready
     
     Returns
     -------
-    kernel, kernel_manager: Popen instance and connected KernelManager
+    kernel_manager: connected KernelManager instance
     """
     kernel = Popen([sys.executable, '-c', cmd], stdout=PIPE, stderr=PIPE, env=env)
     connection_file = os.path.join(IPYTHONDIR,
@@ -81,7 +83,10 b' def _launch_kernel(cmd):'
     km.load_connection_file()
     km.start_channels()
     
-    return kernel, km
+    try:
+        yield km
+    finally:
+        km.stop_channels()
 
 def test_embed_kernel_basic():
     """IPython.embed_kernel() is basically functional"""
@@ -95,7 +100,7 b' def test_embed_kernel_basic():'
         '',
     ])
     
-    kernel, km = _launch_kernel(cmd)
+    with setup_kernel(cmd) as km:
     shell = km.shell_channel
     
     # oinfo a (int)
@@ -128,7 +133,7 b' def test_embed_kernel_namespace():'
         '',
     ])
     
-    kernel, km = _launch_kernel(cmd)
+    with setup_kernel(cmd) as km:
     shell = km.shell_channel
     
     # oinfo a (int)