Jupyter notebook locked traceback

jupyter notebook  --no-browser
/home/alord/.virtualenvs/adhoc_notebooks/lib/python3.4/site-packages/widgetsnbextension/__init__.py:30: UserWarning: To use the jupyter-js-widgets nbextension, you'll need to update
    the Jupyter notebook to version 4.2 or later.al
  the Jupyter notebook to version 4.2 or later.""")
[I 20:11:41.327 NotebookApp] Serving notebooks from local directory: /home/alord/git/adhoc_notebooks/onefs_jobs
[I 20:11:41.327 NotebookApp] 0 active kernels
[I 20:11:41.327 NotebookApp] The Jupyter Notebook is running at: http://****:8888/
[I 20:11:41.327 NotebookApp] Use Control-C to stop this server and shut down all kernels (twice to skip confirmation).
[I 20:11:50.383 NotebookApp] 302 GET / (****) 1.21ms
[E 20:18:01.631 NotebookApp] Unhandled error in API request
    Traceback (most recent call last):
      File "/home/alord/.virtualenvs/adhoc_notebooks/lib/python3.4/site-packages/traitlets/traitlets.py", line 501, in get
        value = obj._trait_values[self.name]
    KeyError: 'db'

    During handling of the above exception, another exception occurred:

    Traceback (most recent call last):
      File "/home/alord/.virtualenvs/adhoc_notebooks/lib/python3.4/site-packages/notebook/base/handlers.py", line 457, in wrapper
        result = yield gen.maybe_future(method(self, *args, **kwargs))
      File "/home/alord/.virtualenvs/adhoc_notebooks/lib/python3.4/site-packages/tornado/gen.py", line 1008, in run
        value = future.result()
      File "/home/alord/.virtualenvs/adhoc_notebooks/lib/python3.4/site-packages/tornado/concurrent.py", line 232, in result
        raise_exc_info(self._exc_info)
      File "<string>", line 3, in raise_exc_info
      File "/home/alord/.virtualenvs/adhoc_notebooks/lib/python3.4/site-packages/tornado/gen.py", line 282, in wrapper
        yielded = next(result)
      File "/home/alord/.virtualenvs/adhoc_notebooks/lib/python3.4/site-packages/notebook/services/contents/handlers.py", line 124, in get
        path=path, type=type, format=format, content=content,
      File "/home/alord/.virtualenvs/adhoc_notebooks/lib/python3.4/site-packages/notebook/services/contents/filemanager.py", line 358, in get
        model = self._notebook_model(path, content=content)
      File "/home/alord/.virtualenvs/adhoc_notebooks/lib/python3.4/site-packages/notebook/services/contents/filemanager.py", line 318, in _notebook_model
        self.mark_trusted_cells(nb, path)
      File "/home/alord/.virtualenvs/adhoc_notebooks/lib/python3.4/site-packages/notebook/services/contents/manager.py", line 447, in mark_trusted_cells
        trusted = self.notary.check_signature(nb)
      File "/home/alord/.virtualenvs/adhoc_notebooks/lib/python3.4/site-packages/nbformat/sign.py", line 220, in check_signature
        if self.db is None:
      File "/home/alord/.virtualenvs/adhoc_notebooks/lib/python3.4/site-packages/traitlets/traitlets.py", line 529, in __get__
        return self.get(obj, cls)
      File "/home/alord/.virtualenvs/adhoc_notebooks/lib/python3.4/site-packages/traitlets/traitlets.py", line 508, in get
        value = self._validate(obj, dynamic_default())
      File "/home/alord/.virtualenvs/adhoc_notebooks/lib/python3.4/site-packages/nbformat/sign.py", line 127, in _db_default
        self.init_db(db)
      File "/home/alord/.virtualenvs/adhoc_notebooks/lib/python3.4/site-packages/nbformat/sign.py", line 139, in init_db
        )""")
    sqlite3.OperationalError: database is locked
[E 20:18:01.643 NotebookApp] {
      "User-Agent": "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_10_5) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/50.0.2661.94 Safari/537.36",
      "X-Requested-With": "XMLHttpRequest",
      "Accept": "application/json, text/javascript, */*; q=0.01",
      "Connection": "keep-alive",
      "Host": "****:8888",
      "Referer": "http://****:8888/notebooks/onefs_job_sources_investigation.ipynb",
      "Accept-Encoding": "gzip, deflate, sdch",
      "Accept-Language": "en-US,en;q=0.8"
    }
[E 20:18:01.643 NotebookApp] 500 GET /api/contents/onefs_job_sources_investigation.ipynb?type=notebook&_=1464293540756 (****) 365785.00ms referer=http://*****:8888/notebooks/onefs_job_sources_investigation.ipynb
[W 20:18:01.655 NotebookApp] 404 GET /nbextensions/widgets/notebook/js/extension.js?v=20160526201140 (****) 10.43ms referer=http://****:8888/notebooks/onefs_job_sources_investigation.ipynb