Error when starting

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I get the following error:

+--------------------------------------------------------------------+
| Sage Version 5.11, Release Date: 2013-08-13                        |
| Type "notebook()" for the browser-based notebook interface.        |
| Type "help()" for help.                                            |
+--------------------------------------------------------------------+
Traceback (most recent call last):
  File "/opt/sage-5.5/local/bin/sage-ipython", line 6, in <module>
    from sage.misc.interpreter import SageTerminalApp
  File "/opt/sage-5.5/local/lib/python2.7/site-packages/sage/misc/interpreter.py", line 98, in <module>
    import IPython.ipapi
ImportError: No module named ipapi

What is the solution?