Fix various pylint violations

+ SchedUtils.py: Do not use `len(SEQUENCE)` to determine if a sequence is empty
+ VatHistory.py: Do not use `len(SEQUENCE)` to determine if a sequence is empty
+ VppCounters.py: Do not use `len(SEQUENCE)` to determine if a sequence is empty
+ Memif.py:
++ Do not use `len(SEQUENCE)` to determine if a sequence is empty
++ Either all return statements in a function should return an expression,
   or none of them should.
++ Update :return: on possible None.
+ Classify.py: Unnecessary "else" after "return"
+ ContainerUtils.py: Useless super delegation in method '__init__'
+ CpuUtils.py: Do not use `len(SEQUENCE)` to determine if a sequence is empty
+ DropRateSearch.py: Either all return statements in a function
  should return an expression, or none of them should.
+ IPv4NodeAddress.py: Do not use `len(SEQUENCE)` to determine if a sequence is empty
++ Also improve docstrings.
+ IPv4Setup.py: Useless super delegation in method '__init__'
+ IPv6Setup.py: Do not use `len(SEQUENCE)` to determine if a sequence is empty
++ Also improve docstrings.
+ IPv6Setup.py: standard import "from ipaddress import IPv6Network"
  should be placed before "from robot.api import logger"
+ MacSwap.py: Trailing newlines
+ NATUtil.py: Do not use `len(SEQUENCE)` to determine if a sequence is empty
+ NodePath.py: Unnecessary "else" after "return"
+ Tap.py: Do not use `len(SEQUENCE)` to determine if a sequence is empty
+ topology.py: Either all return statements in a function
  should return an expression, or none of them should.
+ topology.py: Unnecessary "else" after "return"
++ Do not use `len(SEQUENCE)` to determine if a sequence is empty
++ Improve docstrings
+ DUTSetup.py: Do not use `len(SEQUENCE)` to determine if a sequence is empty
++ Also do not compare int(ret_code) just to access zero-ness.
+ ssh.py: Do not use `len(SEQUENCE)` to determine if a sequence is empty
+ InterfaceUtil.py: Unnecessary "else" after "return"

Change-Id: Iba4244aa79661ee7df15fed5c7c6dbf04dfa88b2
Signed-off-by: Vratko Polak <vrpolak@cisco.com>

1 files changed, 13 insertions, 8 deletions

diff --git a/resources/libraries/python/IPv6Setup.py b/resources/libraries/python/IPv6Setup.py
index e0de406a4a..260c08b198 100644
--- a/resources/libraries/python/IPv6Setup.py
+++ b/resources/libraries/python/IPv6Setup.py
@@ -13,8 +13,8 @@
 
 """Library to set up IPv6 in topology."""
 
-from robot.api import logger
 from ipaddress import IPv6Network
+from robot.api import logger
 
 from resources.libraries.python.ssh import SSH
 from resources.libraries.python.topology import NodeType, Topology
@@ -25,17 +25,22 @@ from resources.libraries.python.VatExecutor import VatTerminal, VatExecutor
 class IPv6Networks(object):
     """IPv6 network iterator.
 
-    :param networks: List of the available IPv6 networks.
-    :type networks: list
+    TODO: Conform to https://docs.python.org/2/library/stdtypes.html#typeiter
     """
+
     def __init__(self, networks):
-        self._networks = list()
+        """Initialize internal list of valid networks.
+
+        :param networks: List of the available IPv6 networks.
+        :type networks: list
+        :raise RuntimeError: If no networks were added.
+        """
+        self._networks = []
         for network in networks:
             net = IPv6Network(unicode(network))
             self._networks.append(net)
-        num = len(self._networks)
-        if num == 0:
-            raise Exception('No IPv6 networks')
+        if not self._networks:
+            raise RuntimeError('No IPv6 networks')
 
     def next_network(self):
         """Get the next element of the iterator.
@@ -44,7 +49,7 @@ class IPv6Networks(object):
         :rtype: IPv6Network object
         :raises StopIteration: If there is no more elements.
         """
-        if len(self._networks):
+        if self._networks:
             return self._networks.pop()
         else:
             raise StopIteration()