Move netifaces to extras

netifaces is a very heavy requirement especially for
python clients, the code that uses netifaces is called
only in exception paths at least now. So let us move
this requirement to extras to reduce the time taken
to install oslo.utils.

Closes-Bug: #1517069
Change-Id: If3430364e49c1c0b1d9f4937bb67900380662728

requirements.txt

@@ -15,5 +15,4 @@ oslo.i18n>=1.5.0 # Apache-2.0
 monotonic>=0.3 # Apache-2.0
 pytz>=2013.6
 netaddr!=0.7.16,>=0.7.12
-netifaces>=0.10.4
 debtcollector>=0.3.0 # Apache-2.0

setup.cfg

@@ -22,6 +22,10 @@ classifier =
 packages =
     oslo_utils
 
+[extras]
+netifaces =
+  netifaces>=0.10.4
+
 [pbr]
 warnerrors = true
 

tox.ini

@@ -4,6 +4,7 @@ envlist = py34,py27,pep8,bandit
 
 [testenv]
 deps = -r{toxinidir}/test-requirements.txt
+       .[netifaces]
 commands = python setup.py testr --slowest --testr-args='{posargs}'
 
 [testenv:pep8]