Move dhcp_release6_supported to runtime checks file

Since one of the main reasons for the sanity check system was to
avoid doing runtime checks, importing a sanity check to do a
runtime check encourages bad behavior. This moves the check to a
new runtime_checks.py file that includes a note encouraging people
to use sanity checks wherever possible.

Change-Id: I06bffe00bb796b4727dca7867a15302582ffcc10

neutron/agent/linux/dhcp.py

@@ -36,7 +36,7 @@ from neutron.agent.common import utils as agent_common_utils
 from neutron.agent.linux import external_process
 from neutron.agent.linux import ip_lib
 from neutron.agent.linux import iptables_manager
-from neutron.cmd.sanity import checks
+from neutron.cmd import runtime_checks as checks
 from neutron.common import constants as n_const
 from neutron.common import utils as common_utils
 from neutron.extensions import extra_dhcp_opt as edo_ext

neutron/cmd/runtime_checks.py

@@ -0,0 +1,37 @@
+# Copyright (c) 2014 OpenStack Foundation.
+# All Rights Reserved.
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+from oslo_log import log as logging
+
+from neutron.agent.linux import utils as agent_utils
+
+LOG = logging.getLogger(__name__)
+
+
+# NOTE: Runtime checks are strongly discouraged in favor of sanity checks
+#       which would be run at system setup time. Please consider writing a
+#       sanity check instead.
+
+
+def dhcp_release6_supported():
+    try:
+        cmd = ['dhcp_release6', '--help']
+        env = {'LC_ALL': 'C'}
+        agent_utils.execute(cmd, addl_env=env)
+    except (OSError, RuntimeError, IndexError, ValueError) as e:
+        LOG.debug("Exception while checking dhcp_release6. "
+                  "Exception: %s", e)
+        return False
+    return True

neutron/cmd/sanity/checks.py

@@ -32,6 +32,7 @@ from neutron.agent.linux import ip_lib
 from neutron.agent.linux import ip_link_support
 from neutron.agent.linux import keepalived
 from neutron.agent.linux import utils as agent_utils
+from neutron.cmd import runtime_checks
 from neutron.common import constants
 from neutron.common import utils as common_utils
 from neutron.plugins.common import constants as const
@@ -217,15 +218,7 @@ def dnsmasq_version_supported():
 
 
 def dhcp_release6_supported():
-    try:
+    return runtime_checks.dhcp_release6_supported()
-        cmd = ['dhcp_release6', '--help']
-        env = {'LC_ALL': 'C'}
-        agent_utils.execute(cmd, addl_env=env)
-    except (OSError, RuntimeError, IndexError, ValueError) as e:
-        LOG.debug("Exception while checking dhcp_release6. "
-                  "Exception: %s", e)
-        return False
-    return True
 
 
 def bridge_firewalling_enabled():