Ipython: IPython Notebook 错误：加载笔记本时出错

在过去的几分钟内，我无法访问之前使用 Python3.4 创建的任何.ipynb文件。 我转到包含这些文件的子目录，输入

ipython3 notebook

当我单击某个.ipynb文件时，出现以下错误：

An unknown error occurred while loading this notebook. This version can load notebook formats v4 or earlier. See the server log for details.

[E 00:19:41.468 NotebookApp] Unhandled error in API request
    Traceback (most recent call last):
      File "/opt/local/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/traitlets/traitlets.py", line 460, 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 "/opt/local/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/notebook/base/handlers.py", line 458, in wrapper
    result = yield gen.maybe_future(method(self, *args, **kwargs))
  File "/opt/local/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/tornado/gen.py", line 1008, in run
    value = future.result()
  File "/opt/local/Library/Frameworks/Python.framework/Versions/3.4/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 "/opt/local/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/tornado/gen.py", line 282, in wrapper
    yielded = next(result)
  File "/opt/local/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/notebook/services/contents/handlers.py", line 124, in get
    path=path, type=type, format=format, content=content,
  File "/opt/local/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/notebook/services/contents/filemanager.py", line 354, in get
    model = self._notebook_model(path, content=content)
  File "/opt/local/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/notebook/services/contents/filemanager.py", line 314, in _notebook_model
    self.mark_trusted_cells(nb, path)
  File "/opt/local/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/notebook/services/contents/manager.py", line 447, in mark_trusted_cells
    trusted = self.notary.check_signature(nb)
  File "/opt/local/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/nbformat/sign.py", line 220, in check_signature
    if self.db is None:
  File "/opt/local/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/traitlets/traitlets.py", line 488, in __get__
    return self.get(obj, cls)
  File "/opt/local/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/traitlets/traitlets.py", line 467, in get
    value = self._validate(obj, dynamic_default())
  File "/opt/local/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/nbformat/sign.py", line 127, in _db_default
    self.init_db(db)
  File "/opt/local/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/nbformat/sign.py", line 139, in init_db
    )""")
sqlite3.DatabaseError: database disk image is malformed

如何解决这个问题？