Make tox.ini tox 4.0.0 compatible

* removed skipdist=True to make sure os-vif is available in the virtual
  env
* removed basepython = python3 as we assume all developer switched to
  python3 in their env already
* removed ignore_basepython_conflict = True as without the basepython
  definition generative targets now work without conflict

Also squashed in the commit fixing the functional target as both fix is
needed to unblock the gate:

add CAP_DAC_OVERRIDE to test privsep contexts

This change modifes the privsep contexts used by the test
code to create inteface without using the os-vif plugins.

The os-vif functional tests actully create ovs and linux
brdiges and dummy netdevs. to ensure the drier work correctly
the functional tests have a simpler test only version of the
port/brige management commands that are used to prepare
and validate the test env. The simpler implementation uses
standard linux commandline tools like "ip" or "ovs-vsctl"
which on ubuntu 22.04 require the addtion of CAP_DAC_OVERRIDE
to work around socket/file ownership issues.

To avoid  adding capablities at runtime that are not required
this change modifes the existing test only context in
the os_vif.tests.functional.privsep module and add a new test
context for the vif_plug_ovs plugin

Change-Id: Ide357cb64a8d128ff8ad978abae6a039e814d8a9

os_vif/tests/functional/privsep.py

@@ -17,5 +17,5 @@ os_vif_pctxt = priv_context.PrivContext(
     'os_vif',
     cfg_section='os_vif_privileged',
     pypath=__name__ + '.os_vif_pctxt',
-    capabilities=[c.CAP_NET_ADMIN],
+    capabilities=[c.CAP_NET_ADMIN, c.CAP_DAC_OVERRIDE],
 )

tox.ini

@@ -1,11 +1,8 @@
 [tox]
 minversion = 3.18.0
 envlist = py3,pep8,docs,releasenotes,cover
-skipsdist = True
-ignore_basepython_conflict = True
 
 [testenv]
-basepython = python3
 usedevelop = True
 setenv =
 deps =
@@ -88,5 +85,7 @@ import_exceptions = os_vif.i18n
 # system dependencies are missing, since it's used to tell you what system
 # dependencies are missing! This also means that bindep must be installed
 # separately, outside of the requirements files.
+skipsdist=True
+usedevelop=False
 deps = bindep
 commands = bindep test

vif_plug_ovs/privsep.py

@@ -20,5 +20,16 @@ vif_plug = priv_context.PrivContext(
     "vif_plug_ovs",
     cfg_section="vif_plug_ovs_privileged",
     pypath=__name__ + ".vif_plug",
-    capabilities=[c.CAP_NET_ADMIN],
+    capabilities=[
+        c.CAP_NET_ADMIN,
+    ],
+)
+
+vif_plug_test = priv_context.PrivContext(
+    "vif_plug_ovs",
+    cfg_section="vif_plug_ovs_privileged",
+    pypath=__name__ + ".vif_plug_test",
+    capabilities=[
+        c.CAP_NET_ADMIN, c.CAP_DAC_OVERRIDE,
+    ],
 )

vif_plug_ovs/tests/functional/ovsdb/test_ovsdb_lib.py

@@ -32,7 +32,7 @@ from vif_plug_ovs.tests.functional import base
 CONF = cfg.CONF
 
 
-@privsep.vif_plug.entrypoint
+@privsep.vif_plug_test.entrypoint
 def run_privileged(*full_args):
     return processutils.execute(*full_args)[0].rstrip()