Made help string a class var.

mininet/cli.py

@@ -76,9 +76,6 @@ class CLI( Cmd ):
     # must have the same interface
     # pylint: disable-msg=W0613,R0201
 
-    def do_help( self, args ):
-        "Describe available CLI commands."
-        Cmd.do_help( self, args )
     helpStr = ( 
         'You may also send a command to a node using:\n'
         '  <node> command {args}\n'
@@ -92,13 +89,17 @@ class CLI( Cmd ):
         'should work.\n'
         '\n'
         'Some character-oriented interactive commands require\n'
-            'noecho, e.g.\n'
+        'noecho:\n'
         '  mininet> noecho h2 vi foo.py\n'
         'However, starting up an xterm/gterm is generally better:\n'
         '  mininet> xterm h2\n\n'
     )
+
+    def do_help( self, args ):
+        "Describe available CLI commands."
+        Cmd.do_help( self, args )
         if args is '':
-            output( helpStr )
+            output( self.helpStr )
 
     def do_nodes( self, args ):
         "List all nodes."