test_get_free_namespace_port fails on systems without sysctl

[Corey Wright]

If the unit test test_get_free_namespace_port runs on a system without sysctl, then the test fails as it tries to execute sysctl, because sysctl doesn't exist.

======================================================================
FAIL: neutron.tests.unit.tests.common.test_net_helpers.PortAllocationTestCase.test_get_free_namespace_port
neutron.tests.unit.tests.common.test_net_helpers.PortAllocationTestCase.test_get_free_namespace_port
----------------------------------------------------------------------
_StringException: Empty attachments:
  pythonlogging:''
  stderr
  stdout

Traceback (most recent call last):
  File "neutron/tests/unit/tests/common/test_net_helpers.py", line 65, in test_get_free_namespace_port
    n_const.PROTO_NAME_TCP)
  File "neutron/tests/common/net_helpers.py", line 215, in get_free_namespace_port
    return get_unused_port(used_ports)
  File "neutron/tests/common/net_helpers.py", line 186, in get_unused_port
    ['sysctl', '-n', 'net.ipv4.ip_local_port_range'])
  File "neutron/agent/linux/utils.py", line 117, in execute
    addl_env=addl_env)
  File "neutron/agent/linux/utils.py", line 87, in create_process
    stderr=subprocess.PIPE)
  File "neutron/common/utils.py", line 85, in subprocess_popen
    close_fds=close_fds, env=env)
  File "/var/lib/jenkins/workspace/test-neutron-rax-patches-change/virtualenv/local/lib/python2.7/site-packages/eventlet/green/subprocess.py", line 53, in __init__
    subprocess_orig.Popen.__init__(self, args, 0, *argss, **kwds)
  File "/usr/lib/python2.7/subprocess.py", line 679, in __init__
    errread, errwrite)
  File "/usr/lib/python2.7/subprocess.py", line 1259, in _execute_child
    raise child_exception
OSError: [Errno 2] No such file or directory

Code under test shouldn't be allowed to execute local commands for multiple reasons:
0. a test system is not a deployment system
1. the command might not exist
2. the command's output might be system-dependent
3. the command might unintentionally alter the state of the system

The execution of sysctl should be mocked.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/363917

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/363917
Committed: https://git.openstack.org/cgit/openstack/neutron/commit/?id=5e4204804ea4b364d27d014d13ecb529bc370ea6
Submitter: Jenkins
Branch: master

commit 5e4204804ea4b364d27d014d13ecb529bc370ea6
Author: Corey Wright <email address hidden>
Date: Wed Aug 31 14:34:13 2016 -0500

    Mock call to sysctl for test_get_free_namespace_port

    The code under test shouldn't execute local commands for multiple
    reasons (eg the command doesn't exist on the test system), so mock out
    the execution of sysctl in test_get_free_namespace_port (copying the
    code from test_get_unused_port).

    Change-Id: I58aa578274310ae2ca015069f99edb84716fb0b5
    Closes-bug: #1619028

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/neutron 9.0.0.0b3 development milestone.