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I used to be able to use the Sage 5.10 notebook (installed from the Ubuntu ppa) without any problems. Now, when I type sage at the command prompt and start the notebook the notebook opens fine and I can see and edit my previous worksheets.

However, I can't evaluate any cells or use tab-completion. Eg, if I create a new worksheet and type E = EllipticCurve("11a") or if I type E = Ellipt and then hit [tab] the worksheet just stalls indefinitely. The sage console displays some errors. I tried searching around but I couldn't find anything like it online. I get the same errors after upgrading to version 5.11, and from using a copy of sage downloaded from the sagemath.org website instead of the Ubuntu ppa.

The notebook files are stored in: sage_notebook.sagenb
 
 
 
*
 
Open your web browser to http://localhost:8080 *
 
*
 
 
 
Executing twistd  --pidfile="sage_notebook.sagenb/sagenb.pid" -ny "sage_notebook.sagenb/twistedconf.tac"
2013-08-17 13:19:21-0500 [-] Log opened.
2013-08-17 13:19:21-0500 [-] twistd 12.3.0 (/usr/lib/sagemath/local/bin/python 2.7.5) starting up.
2013-08-17 13:19:21-0500 [-] reactor class: twisted.internet.epollreactor.EPollReactor.
2013-08-17 13:19:21-0500 [-] QuietSite starting on 8080
2013-08-17 13:19:21-0500 [-] Starting factory <__builtin__.QuietSite instance at 0x6e96ab8>
 
(process:3245): GLib-CRITICAL *: g_slice_set_config: assertion `sys_page_size == 0' failed
2013-08-17 13:19:44-0500 [-] WSGI application error
    Traceback (most recent call last):
      File "/usr/lib/sagemath/local/lib/python2.7/site-packages/Twisted-12.3.0-py2.7-linux-x86_64.egg/twisted/python/threadpool.py", line 195, in _worker
        o = self.q.get()
      File "/usr/lib/sagemath/local/lib/python2.7/site-packages/Twisted-12.3.0-py2.7-linux-x86_64.egg/twisted/python/context.py", line 118, in callWithContext
        return self.currentContext().callWithContext(ctx, func, *args, *kw)
      File "/usr/lib/sagemath/local/lib/python2.7/site-packages/Twisted-12.3.0-py2.7-linux-x86_64.egg/twisted/python/context.py", line 83, in callWithContext
        self.contexts.pop()
      File "/usr/lib/sagemath/local/lib/python2.7/site-packages/Twisted-12.3.0-py2.7-linux-x86_64.egg/twisted/web/wsgi.py", line 340, in run
        self.started = True
    --- <exception caught="" here=""> ---
      File "/usr/lib/sagemath/local/lib/python2.7/site-packages/Twisted-12.3.0-py2.7-linux-x86_64.egg/twisted/web/wsgi.py", line 315, in run
        appIterator = self.application(self.environ, self.startResponse)
      File "/usr/lib/sagemath/local/lib/python2.7/site-packages/Flask-0.9-py2.7.egg/flask/app.py", line 1701, in __call__
        return self.wsgi_app(environ, start_response)
      File "/usr/lib/sagemath/local/lib/python2.7/site-packages/Flask-0.9-py2.7.egg/flask/app.py", line 1689, in wsgi_app
        response = self.make_response(self.handle_exception(e))
      File "/usr/lib/sagemath/local/lib/python2.7/site-packages/Flask-0.9-py2.7.egg/flask/app.py", line 1687, in wsgi_app
        response = self.full_dispatch_request()
      File "/usr/lib/sagemath/local/lib/python2.7/site-packages/Flask-0.9-py2.7.egg/flask/app.py", line 1360, in full_dispatch_request
        rv = self.handle_user_exception(e)
      File "/usr/lib/sagemath/local/lib/python2.7/site-packages/Flask-0.9-py2.7.egg/flask/app.py", line 1358, in full_dispatch_request
        rv = self.dispatch_request()
      File "/usr/lib/sagemath/local/lib/python2.7/site-packages/Flask-0.9-py2.7.egg/flask/app.py", line 1344, in dispatch_request
        return self.view_functionsrule.endpoint
      File "/usr/lib/sagemath/devel/sagenb/flask_version/decorators.py", line 22, in wrapper
        return f(args, *kwds)
      File "/usr/lib/sagemath/devel/sagenb/flask_version/worksheet.py", line 46, in wrapper
        return f(username, id, *kwds)
      File "/usr/lib/sagemath/devel/sagenb/flask_version/worksheet.py", line 134, in wrapper
        return f(args, **kwds)
      File "/usr/lib/sagemath/devel/sagenb/flask_version/worksheet.py", line 457, in worksheet_cell_update
        g.notebook.add_to_user_history(H, g.username)
      File "/usr/lib/sagemath/devel/sagenb/sagenb/notebook/notebook.py", line 712, in add_to_user_history
        history = self.user_history(username)
      File "/usr/lib/sagemath/devel/sagenb/sagenb/notebook/notebook.py", line 694, in user_history
        for hunk in self.__storage.load_user_history(username):
      File "/usr/lib/sagemath/devel/sagenb/sagenb/storage/filesystem_storage.py", line 311, in load_user_history
        return self._load(filename)
      File "/usr/lib/sagemath/devel/sagenb/sagenb/storage/filesystem_storage.py", line 167, in _load
        result = cPickle.load(f)
    exceptions.EOFError: 
 
2013-08-17 13:19:45-0500 [-] WSGI application error
    Traceback (most recent call last):
      File "/usr/lib/sagemath/local/lib/python2.7/site-packages/Twisted-12.3.0-py2.7-linux-x86_64.egg/twisted/python/threadpool.py", line 195, in _worker
        o = self.q.get()
      File "/usr/lib/sagemath/local/lib/python2.7/site-packages/Twisted-12.3.0-py2.7-linux-x86_64.egg/twisted/python/context.py", line 118, in callWithContext
        return self.currentContext().callWithContext(ctx, func, args, *kw)
      File "/usr/lib/sagemath/local/lib/python2.7/site-packages/Twisted-12.3.0-py2.7-linux-x86_64.egg/twisted/python/context.py", line 83, in callWithContext
        self.contexts.pop()
      File "/usr/lib/sagemath/local/lib/python2.7/site-packages/Twisted-12.3.0-py2.7-linux-x86_64.egg/twisted/web/wsgi.py", line 340, in run
        self.started = True
    --- <exception caught="" here=""> ---
      File "/usr/lib/sagemath/local/lib/python2.7/site-packages/Twisted-12.3.0-py2.7-linux-x86_64.egg/twisted/web/wsgi.py", line 315, in run
        appIterator = self.application(self.environ, self.startResponse)
      File "/usr/lib/sagemath/local/lib/python2.7/site-packages/Flask-0.9-py2.7.egg/flask/app.py", line 1701, in __call__
        return self.wsgi_app(environ, start_response)
      File "/usr/lib/sagemath/local/lib/python2.7/site-packages/Flask-0.9-py2.7.egg/flask/app.py", line 1689, in wsgi_app
        response = self.make_response(self.handle_exception(e))
      File "/usr/lib/sagemath/local/lib/python2.7/site-packages/Flask-0.9-py2.7.egg/flask/app.py", line 1687, in wsgi_app
        response = self.full_dispatch_request()
      File "/usr/lib/sagemath/local/lib/python2.7/site-packages/Flask-0.9-py2.7.egg/flask/app.py", line 1360, in full_dispatch_request
        rv = self.handle_user_exception(e)
      File "/usr/lib/sagemath/local/lib/python2.7/site-packages/Flask-0.9-py2.7.egg/flask/app.py", line 1358, in full_dispatch_request
        rv = self.dispatch_request()
      File "/usr/lib/sagemath/local/lib/python2.7/site-packages/Flask-0.9-py2.7.egg/flask/app.py", line 1344, in dispatch_request
        return self.view_functionsrule.endpoint
      File "/usr/lib/sagemath/devel/sagenb/flask_version/decorators.py", line 22, in wrapper
        return f(args, *kwds)
      File "/usr/lib/sagemath/devel/sagenb/flask_version/worksheet.py", line 46, in wrapper
        return f(username, id, *kwds)
      File "/usr/lib/sagemath/devel/sagenb/flask_version/worksheet.py", line 134, in wrapper
        return f(args, **kwds)
      File "/usr/lib/sagemath/devel/sagenb/flask_version/worksheet.py", line 457, in worksheet_cell_update
        g.notebook.add_to_user_history(H, g.username)
      File "/usr/lib/sagemath/devel/sagenb/sagenb/notebook/notebook.py", line 712, in add_to_user_history
        history = self.user_history(username)
      File "/usr/lib/sagemath/devel/sagenb/sagenb/notebook/notebook.py", line 694, in user_history
        for hunk in self.__storage.load_user_history(username):
      File "/usr/lib/sagemath/devel/sagenb/sagenb/storage/filesystem_storage.py", line 311, in load_user_history
        return self._load(filename)
      File "/usr/lib/sagemath/devel/sagenb/sagenb/storage/filesystem_storage.py", line 167, in _load
        result = cPickle.load(f)
    exceptions.EOFError: 
 
^C2013-08-17 13:19:46-0500 [-] WSGI application error
    Traceback (most recent call last):
      File "/usr/lib/sagemath/local/lib/python2.7/site-packages/Twisted-12.3.0-py2.7-linux-x86_64.egg/twisted/python/threadpool.py", line 195, in _worker
        o = self.q.get()
      File "/usr/lib/sagemath/local/lib/python2.7/site-packages/Twisted-12.3.0-py2.7-linux-x86_64.egg/twisted/python/context.py", line 118, in callWithContext
        return self.currentContext().callWithContext(ctx, func, args, *kw)
      File "/usr/lib/sagemath/local/lib/python2.7/site-packages/Twisted-12.3.0-py2.7-linux-x86_64.egg/twisted/python/context.py", line 83, in callWithContext
        self.contexts.pop()
      File "/usr/lib/sagemath/local/lib/python2.7/site-packages/Twisted-12.3.0-py2.7-linux-x86_64.egg/twisted/web/wsgi.py", line 340, in run
        self.started = True
    --- <exception caught="" here=""> ---
      File "/usr/lib/sagemath/local/lib/python2.7/site-packages/Twisted-12.3.0-py2.7-linux-x86_64.egg/twisted/web/wsgi.py", line 315, in run
        appIterator = self.application(self.environ, self.startResponse)
      File "/usr/lib/sagemath/local/lib/python2.7/site-packages/Flask-0.9-py2.7.egg/flask/app.py", line 1701, in __call__
        return self.wsgi_app(environ, start_response)
      File "/usr/lib/sagemath/local/lib/python2.7/site-packages/Flask-0.9-py2.7.egg/flask/app.py", line 1689, in wsgi_app
        response = self.make_response(self.handle_exception(e))
      File "/usr/lib/sagemath/local/lib/python2.7/site-packages/Flask-0.9-py2.7.egg/flask/app.py", line 1687, in wsgi_app
        response = self.full_dispatch_request()
      File "/usr/lib/sagemath/local/lib/python2.7/site-packages/Flask-0.9-py2.7.egg/flask/app.py", line 1360, in full_dispatch_request
        rv = self.handle_user_exception(e)
      File "/usr/lib/sagemath/local/lib/python2.7/site-packages/Flask-0.9-py2.7.egg/flask/app.py", line 1358, in full_dispatch_request
        rv = self.dispatch_request()
      File "/usr/lib/sagemath/local/lib/python2.7/site-packages/Flask-0.9-py2.7.egg/flask/app.py", line 1344, in dispatch_request
        return self.view_functionsrule.endpoint
      File "/usr/lib/sagemath/devel/sagenb/flask_version/decorators.py", line 22, in wrapper
        return f(args, *kwds)
      File "/usr/lib/sagemath/devel/sagenb/flask_version/worksheet.py", line 46, in wrapper
        return f(username, id, *kwds)
      File "/usr/lib/sagemath/devel/sagenb/flask_version/worksheet.py", line 134, in wrapper
        return f(args, **kwds)
      File "/usr/lib/sagemath/devel/sagenb/flask_version/worksheet.py", line 457, in worksheet_cell_update
        g.notebook.add_to_user_history(H, g.username)
      File "/usr/lib/sagemath/devel/sagenb/sagenb/notebook/notebook.py", line 712, in add_to_user_history
        history = self.user_history(username)
      File "/usr/lib/sagemath/devel/sagenb/sagenb/notebook/notebook.py", line 694, in user_history
        for hunk in self.__storage.load_user_history(username):
      File "/usr/lib/sagemath/devel/sagenb/sagenb/storage/filesystem_storage.py", line 311, in load_user_history
        return self._load(filename)
      File "/usr/lib/sagemath/devel/sagenb/sagenb/storage/filesystem_storage.py", line 167, in _load
        result = cPickle.load(f)
    exceptions.EOFError: 

I used to be able to use the Sage 5.10 notebook (installed from the Ubuntu ppa) without any problems. Now, when I type sage at the command prompt and start the notebook the notebook opens fine and I can see and edit my previous worksheets.

However, I can't evaluate any cells or use tab-completion. Eg, if I create a new worksheet and type E = EllipticCurve("11a") or if I type E = Ellipt and then hit [tab] the worksheet just stalls indefinitely. The sage console displays some errors. I tried searching around but I couldn't find anything like it online. I get the same errors after upgrading to version 5.11, and from using a copy of sage downloaded from the sagemath.org website instead of the Ubuntu ppa.

The notebook files are stored in: sage_notebook.sagenb
 
 
 
*
 
Open your web browser to http://localhost:8080 *
 
*
 
 
 
Executing twistd  --pidfile="sage_notebook.sagenb/sagenb.pid" -ny "sage_notebook.sagenb/twistedconf.tac"
2013-08-17 13:19:21-0500 [-] Log opened.
2013-08-17 13:19:21-0500 [-] twistd 12.3.0 (/usr/lib/sagemath/local/bin/python 2.7.5) starting up.
2013-08-17 13:19:21-0500 [-] reactor class: twisted.internet.epollreactor.EPollReactor.
2013-08-17 13:19:21-0500 [-] QuietSite starting on 8080
2013-08-17 13:19:21-0500 [-] Starting factory <__builtin__.QuietSite instance at 0x6e96ab8>
 
(process:3245): GLib-CRITICAL *: g_slice_set_config: assertion `sys_page_size == 0' failed
2013-08-17 13:19:44-0500 [-] WSGI application error
    Traceback (most recent call last):
      File "/usr/lib/sagemath/local/lib/python2.7/site-packages/Twisted-12.3.0-py2.7-linux-x86_64.egg/twisted/python/threadpool.py", line 195, in _worker
        o = self.q.get()
      File "/usr/lib/sagemath/local/lib/python2.7/site-packages/Twisted-12.3.0-py2.7-linux-x86_64.egg/twisted/python/context.py", line 118, in callWithContext
        return self.currentContext().callWithContext(ctx, func, *args, *kw)
      File "/usr/lib/sagemath/local/lib/python2.7/site-packages/Twisted-12.3.0-py2.7-linux-x86_64.egg/twisted/python/context.py", line 83, in callWithContext
        self.contexts.pop()
      File "/usr/lib/sagemath/local/lib/python2.7/site-packages/Twisted-12.3.0-py2.7-linux-x86_64.egg/twisted/web/wsgi.py", line 340, in run
        self.started = True
    --- <exception caught="" here=""> ---
      File "/usr/lib/sagemath/local/lib/python2.7/site-packages/Twisted-12.3.0-py2.7-linux-x86_64.egg/twisted/web/wsgi.py", line 315, in run
        appIterator = self.application(self.environ, self.startResponse)
      File "/usr/lib/sagemath/local/lib/python2.7/site-packages/Flask-0.9-py2.7.egg/flask/app.py", line 1701, in __call__
        return self.wsgi_app(environ, start_response)
      File "/usr/lib/sagemath/local/lib/python2.7/site-packages/Flask-0.9-py2.7.egg/flask/app.py", line 1689, in wsgi_app
        response = self.make_response(self.handle_exception(e))
      File "/usr/lib/sagemath/local/lib/python2.7/site-packages/Flask-0.9-py2.7.egg/flask/app.py", line 1687, in wsgi_app
        response = self.full_dispatch_request()
      File "/usr/lib/sagemath/local/lib/python2.7/site-packages/Flask-0.9-py2.7.egg/flask/app.py", line 1360, in full_dispatch_request
        rv = self.handle_user_exception(e)
      File "/usr/lib/sagemath/local/lib/python2.7/site-packages/Flask-0.9-py2.7.egg/flask/app.py", line 1358, in full_dispatch_request
        rv = self.dispatch_request()
      File "/usr/lib/sagemath/local/lib/python2.7/site-packages/Flask-0.9-py2.7.egg/flask/app.py", line 1344, in dispatch_request
        return self.view_functionsrule.endpoint
      File "/usr/lib/sagemath/devel/sagenb/flask_version/decorators.py", line 22, in wrapper
        return f(args, *kwds)
      File "/usr/lib/sagemath/devel/sagenb/flask_version/worksheet.py", line 46, in wrapper
        return f(username, id, *kwds)
      File "/usr/lib/sagemath/devel/sagenb/flask_version/worksheet.py", line 134, in wrapper
        return f(args, **kwds)
      File "/usr/lib/sagemath/devel/sagenb/flask_version/worksheet.py", line 457, in worksheet_cell_update
        g.notebook.add_to_user_history(H, g.username)
      File "/usr/lib/sagemath/devel/sagenb/sagenb/notebook/notebook.py", line 712, in add_to_user_history
        history = self.user_history(username)
      File "/usr/lib/sagemath/devel/sagenb/sagenb/notebook/notebook.py", line 694, in user_history
        for hunk in self.__storage.load_user_history(username):
      File "/usr/lib/sagemath/devel/sagenb/sagenb/storage/filesystem_storage.py", line 311, in load_user_history
        return self._load(filename)
      File "/usr/lib/sagemath/devel/sagenb/sagenb/storage/filesystem_storage.py", line 167, in _load
        result = cPickle.load(f)
    exceptions.EOFError: 
 
2013-08-17 13:19:45-0500 [-] WSGI application error
    Traceback (most recent call last):
      File "/usr/lib/sagemath/local/lib/python2.7/site-packages/Twisted-12.3.0-py2.7-linux-x86_64.egg/twisted/python/threadpool.py", line 195, in _worker
        o = self.q.get()
      File "/usr/lib/sagemath/local/lib/python2.7/site-packages/Twisted-12.3.0-py2.7-linux-x86_64.egg/twisted/python/context.py", line 118, in callWithContext
        return self.currentContext().callWithContext(ctx, func, args, *kw)
      File "/usr/lib/sagemath/local/lib/python2.7/site-packages/Twisted-12.3.0-py2.7-linux-x86_64.egg/twisted/python/context.py", line 83, in callWithContext
        self.contexts.pop()
      File "/usr/lib/sagemath/local/lib/python2.7/site-packages/Twisted-12.3.0-py2.7-linux-x86_64.egg/twisted/web/wsgi.py", line 340, in run
        self.started = True
    --- <exception caught="" here=""> ---
      File "/usr/lib/sagemath/local/lib/python2.7/site-packages/Twisted-12.3.0-py2.7-linux-x86_64.egg/twisted/web/wsgi.py", line 315, in run
        appIterator = self.application(self.environ, self.startResponse)
      File "/usr/lib/sagemath/local/lib/python2.7/site-packages/Flask-0.9-py2.7.egg/flask/app.py", line 1701, in __call__
        return self.wsgi_app(environ, start_response)
      File "/usr/lib/sagemath/local/lib/python2.7/site-packages/Flask-0.9-py2.7.egg/flask/app.py", line 1689, in wsgi_app
        response = self.make_response(self.handle_exception(e))
      File "/usr/lib/sagemath/local/lib/python2.7/site-packages/Flask-0.9-py2.7.egg/flask/app.py", line 1687, in wsgi_app
        response = self.full_dispatch_request()
      File "/usr/lib/sagemath/local/lib/python2.7/site-packages/Flask-0.9-py2.7.egg/flask/app.py", line 1360, in full_dispatch_request
        rv = self.handle_user_exception(e)
      File "/usr/lib/sagemath/local/lib/python2.7/site-packages/Flask-0.9-py2.7.egg/flask/app.py", line 1358, in full_dispatch_request
        rv = self.dispatch_request()
      File "/usr/lib/sagemath/local/lib/python2.7/site-packages/Flask-0.9-py2.7.egg/flask/app.py", line 1344, in dispatch_request
        return self.view_functionsrule.endpoint
      File "/usr/lib/sagemath/devel/sagenb/flask_version/decorators.py", line 22, in wrapper
        return f(args, *kwds)
      File "/usr/lib/sagemath/devel/sagenb/flask_version/worksheet.py", line 46, in wrapper
        return f(username, id, *kwds)
      File "/usr/lib/sagemath/devel/sagenb/flask_version/worksheet.py", line 134, in wrapper
        return f(args, **kwds)
      File "/usr/lib/sagemath/devel/sagenb/flask_version/worksheet.py", line 457, in worksheet_cell_update
        g.notebook.add_to_user_history(H, g.username)
      File "/usr/lib/sagemath/devel/sagenb/sagenb/notebook/notebook.py", line 712, in add_to_user_history
        history = self.user_history(username)
      File "/usr/lib/sagemath/devel/sagenb/sagenb/notebook/notebook.py", line 694, in user_history
        for hunk in self.__storage.load_user_history(username):
      File "/usr/lib/sagemath/devel/sagenb/sagenb/storage/filesystem_storage.py", line 311, in load_user_history
        return self._load(filename)
      File "/usr/lib/sagemath/devel/sagenb/sagenb/storage/filesystem_storage.py", line 167, in _load
        result = cPickle.load(f)
    exceptions.EOFError: 
 
^C2013-08-17 13:19:46-0500 [-] WSGI application error
    Traceback (most recent call last):
      File "/usr/lib/sagemath/local/lib/python2.7/site-packages/Twisted-12.3.0-py2.7-linux-x86_64.egg/twisted/python/threadpool.py", line 195, in _worker
        o = self.q.get()
      File "/usr/lib/sagemath/local/lib/python2.7/site-packages/Twisted-12.3.0-py2.7-linux-x86_64.egg/twisted/python/context.py", line 118, in callWithContext
        return self.currentContext().callWithContext(ctx, func, args, *kw)
      File "/usr/lib/sagemath/local/lib/python2.7/site-packages/Twisted-12.3.0-py2.7-linux-x86_64.egg/twisted/python/context.py", line 83, in callWithContext
        self.contexts.pop()
      File "/usr/lib/sagemath/local/lib/python2.7/site-packages/Twisted-12.3.0-py2.7-linux-x86_64.egg/twisted/web/wsgi.py", line 340, in run
        self.started = True
    --- <exception caught="" here=""> ---
      File "/usr/lib/sagemath/local/lib/python2.7/site-packages/Twisted-12.3.0-py2.7-linux-x86_64.egg/twisted/web/wsgi.py", line 315, in run
        appIterator = self.application(self.environ, self.startResponse)
      File "/usr/lib/sagemath/local/lib/python2.7/site-packages/Flask-0.9-py2.7.egg/flask/app.py", line 1701, in __call__
        return self.wsgi_app(environ, start_response)
      File "/usr/lib/sagemath/local/lib/python2.7/site-packages/Flask-0.9-py2.7.egg/flask/app.py", line 1689, in wsgi_app
        response = self.make_response(self.handle_exception(e))
      File "/usr/lib/sagemath/local/lib/python2.7/site-packages/Flask-0.9-py2.7.egg/flask/app.py", line 1687, in wsgi_app
        response = self.full_dispatch_request()
      File "/usr/lib/sagemath/local/lib/python2.7/site-packages/Flask-0.9-py2.7.egg/flask/app.py", line 1360, in full_dispatch_request
        rv = self.handle_user_exception(e)
      File "/usr/lib/sagemath/local/lib/python2.7/site-packages/Flask-0.9-py2.7.egg/flask/app.py", line 1358, in full_dispatch_request
        rv = self.dispatch_request()
      File "/usr/lib/sagemath/local/lib/python2.7/site-packages/Flask-0.9-py2.7.egg/flask/app.py", line 1344, in dispatch_request
        return self.view_functionsrule.endpoint
      File "/usr/lib/sagemath/devel/sagenb/flask_version/decorators.py", line 22, in wrapper
        return f(args, *kwds)
      File "/usr/lib/sagemath/devel/sagenb/flask_version/worksheet.py", line 46, in wrapper
        return f(username, id, *kwds)
      File "/usr/lib/sagemath/devel/sagenb/flask_version/worksheet.py", line 134, in wrapper
        return f(args, **kwds)
      File "/usr/lib/sagemath/devel/sagenb/flask_version/worksheet.py", line 457, in worksheet_cell_update
        g.notebook.add_to_user_history(H, g.username)
      File "/usr/lib/sagemath/devel/sagenb/sagenb/notebook/notebook.py", line 712, in add_to_user_history
        history = self.user_history(username)
      File "/usr/lib/sagemath/devel/sagenb/sagenb/notebook/notebook.py", line 694, in user_history
        for hunk in self.__storage.load_user_history(username):
      File "/usr/lib/sagemath/devel/sagenb/sagenb/storage/filesystem_storage.py", line 311, in load_user_history
        return self._load(filename)
      File "/usr/lib/sagemath/devel/sagenb/sagenb/storage/filesystem_storage.py", line 167, in _load
        result = cPickle.load(f)
    exceptions.EOFError: