A global isort fix.

Not sure how these got past CI.

Testing Done:
Noticed these borked files in an unrelated branch.

I ran `./build-support/bin/isort.sh -f` to generate
this diff in full.

CI is away here:
  https://travis-ci.org/pantsbuild/pants/builds/72036259

Bugs closed: 1846

Reviewed at https://rbcommons.com/s/twitter/r/2510/

src/python/pants/backend/jvm/tasks/ivy_task_mixin.py

@@ -309,4 +309,3 @@ def _get_ivy_args(mapdir):
       '-symlink',
       ]
     return ivy_args
-

src/python/pants/java/nailgun_executor.py

@@ -14,15 +14,15 @@
 import time
 from collections import namedtuple
 
+from six import string_types
+from twitter.common.collections import maybe_list
+
 from pants.base.build_environment import get_buildroot
 from pants.java.executor import Executor, SubprocessExecutor
 from pants.java.nailgun_client import NailgunClient
 from pants.pantsd.process_manager import ProcessGroup, ProcessManager
 from pants.util.dirutil import safe_open
 
-from six import string_types
-from twitter.common.collections import maybe_list
-
 
 logger = logging.getLogger(__name__)
 

src/python/pants/pantsd/process_manager.py

@@ -5,19 +5,19 @@
 from __future__ import (absolute_import, division, generators, nested_scopes, print_function,
                         unicode_literals, with_statement)
 
-from contextlib import contextmanager
 import logging
 import os
 import signal
 import subprocess
 import time
 import traceback
+from contextlib import contextmanager
+
+import psutil
 
 from pants.base.build_environment import get_buildroot
 from pants.util.dirutil import safe_delete, safe_mkdir, safe_open
 
-import psutil
-
 
 logger = logging.getLogger(__name__)
 

tests/python/pants_test/pantsd/test_process_manager.py

@@ -5,17 +5,17 @@
 from __future__ import (absolute_import, division, generators, nested_scopes, print_function,
                         unicode_literals, with_statement)
 
-from collections import namedtuple
 import os
 import subprocess
 import unittest
-
-from pants.pantsd.process_manager import ProcessGroup, ProcessManager
-from pants.util.contextutil import temporary_dir
+from collections import namedtuple
 
 import mock
 import psutil
 
+from pants.pantsd.process_manager import ProcessGroup, ProcessManager
+from pants.util.contextutil import temporary_dir
+
 
 PATCH_OPTS = dict(autospec=True, spec_set=True)