'**DEPRECATED**: Get the most recent error on this database.
This method is obsolete: all MongoDB write operations (insert, update,
remove, and so on) use the write concern ``w=1`` and report their
errors by default.
Only returns errors that have occurred since the last call to
:meth:`reset_error_history`. Returns None if no such errors have
occurred.
.. versionchanged:: 2.8
Deprecated.'

def previous_error(self):

    warnings.warn('previous_error()    is    deprecated', DeprecationWarning, stacklevel=2)
    error = self.command('getpreverror')
    if (error.get('err', 0) is None):
        return None
    return error
