title: Jython 2.7.0 jump command not working
body: <p>I tried to execute "jump" command of pdb lib. I'm using Jython (in a Java application). Command comes with this error: </p>
  
  <pre><code>    Traceback (most recent call last):
    File "C:\pdb_jump.py", line 20, in &lt;module&gt;
      result = []
    File "C:\jython\Lib\bdb.py", line 49, in trace_dispatch
      return self.dispatch_line(frame)
    File "C:\jython\Lib\bdb.py", line 67, in dispatch_line
      self.user_line(frame)
    File "C:\jython\Lib\pdb.py", line 158, in user_line
      self.interaction(frame, None)
    File "C:\jython\Lib\pdb.py", line 210, in interaction
      self.cmdloop()
    File "C:\jython\Lib\cmd.py", line 142, in cmdloop
      stop = self.onecmd(line)
    File "C:\jython\Lib\pdb.py", line 279, in onecmd
      return cmd.Cmd.onecmd(self, line)
    File "C:\jython\Lib\cmd.py", line 221, in onecmd
      return func(arg)
    File "C:\jython\Lib\pdb.py", line 705, in do_jump
      self.curframe.f_lineno = arg
    File "C:\jython\Lib\pdb.py", line 705, in do_jump
      self.curframe.f_lineno = arg
  TypeError: readonly attribute
  </code></pre>
  
  <p>It seems "jump" command does not work. arg type is integer and this value cannot be set to "self.curframe.f_lineno". What should I do? Any suggestion?</p>
  
  <p>Java version: 1.8 64-bit, Jython versin: 2.7</p>