print -> info; end the horror of print vs. print()

Although we could use print() from __future__, this messes
up scripts which use examples as modules.

The simple, if not nicest for 2.7, solution is to use
info(), output() and other mininet.log functions. The disadvantage
is that we may have to adjust things if we change info() to
add automatic newlines, but we can burn that bridge in Mininet
3.x.

examples/treeping64.py

@@ -3,7 +3,7 @@
 "Create a 64-node tree network, and test connectivity using ping."
 
 
-from mininet.log import setLogLevel
+from mininet.log import setLogLevel, info
 from mininet.node import UserSwitch, OVSKernelSwitch  # , KernelSwitch
 from mininet.topolib import TreeNet
 
@@ -16,17 +16,16 @@ def treePing64():
                   'Open vSwitch kernel': OVSKernelSwitch }
 
     for name in switches:
-        print( "*** Testing", name, "datapath" )
+        info( "*** Testing", name, "datapath\n" )
         switch = switches[ name ]
         network = TreeNet( depth=2, fanout=8, switch=switch )
         result = network.run( network.pingAll )
         results[ name ] = result
 
-    print()
-    print( "*** Tree network ping results:" )
+    info( "\n*** Tree network ping results:\n" )
     for name in switches:
-        print( "%s: %d%% packet loss" % ( name, results[ name ] ) )
-    print()
+        info( "%s: %d%% packet loss\n" % ( name, results[ name ] ) )
+    info( '\n' )
 
 if __name__ == '__main__':
     setLogLevel( 'info' )