ubuntu 14 code check fixes so travis can pass (#1006)

examples/treeping64.py

@@ -4,7 +4,7 @@
 
 
 from mininet.log import setLogLevel, info
-from mininet.node import UserSwitch, OVSKernelSwitch, Host, Controller
+from mininet.node import UserSwitch, OVSKernelSwitch, Host
 from mininet.topolib import TreeNet
 
 
@@ -18,8 +18,6 @@ class HostV4( Host ):
             self.cmd( 'sysctl -w net.ipv6.conf.' + cfg )
 
 
-
-
 def treePing64():
     "Run ping test on 64-node tree networks."
 

mininet/cli.py

@@ -399,7 +399,7 @@ class CLI( Cmd ):
                 error( 'invalid command: '
                        'switch <switch name> {start, stop}\n' )
 
-    def do_wait( self, line ):
+    def do_wait( self, _line ):
         "Wait until all switches have connected to a controller"
         self.mn.waitConnected()
 

mininet/nodelib.py

@@ -136,8 +136,6 @@ class NAT( Node ):
         # Instruct the kernel to perform forwarding
         self.cmd( 'sysctl net.ipv4.ip_forward=1' )
 
-
-
     def terminate( self ):
         "Stop NAT/forwarding between Mininet and external network"
         # Remote NAT rules

mininet/test/test_walkthrough.py

@@ -29,8 +29,8 @@ class testWalkthrough( unittest.TestCase ):
 
     prompt = 'mininet>'
 
-
-    def setup( self ):
+    @staticmethod
+    def setup():
         "Be paranoid and run cleanup() before each test"
         cleanup()