fix `kernel_info_reply` (missing status)

[n-riesco]

See #212 and jupyterlab/jupyterlab#6860

From https://jupyter-client.readthedocs.io/en/stable/messaging.html#kernel-info

content = {
    # 'ok' if the request succeeded or 'error', with error information as in all other replies.
    'status' : 'ok',

    # Version of messaging protocol.
    # The first integer indicates major version.  It is incremented when
    # there is any backward incompatible change.
    # The second integer indicates minor version.  It is incremented when
    # there is any backward compatible change.
    'protocol_version': 'X.Y.Z',

    # The kernel implementation name
    # (e.g. 'ipython' for the IPython kernel)
    'implementation': str,

    # Implementation version number.
    # The version number of the kernel's implementation
    # (e.g. IPython.__version__ for the IPython kernel)
    'implementation_version': 'X.Y.Z',

    # Information about the language of code for the kernel
    'language_info': {
        # Name of the programming language that the kernel implements.
        # Kernel included in IPython returns 'python'.
        'name': str,

        # Language version number.
        # It is Python version number (e.g., '2.7.3') for the kernel
        # included in IPython.
        'version': 'X.Y.Z',

        # mimetype for script files in this language
        'mimetype': str,

        # Extension including the dot, e.g. '.py'
        'file_extension': str,

        # Pygments lexer, for highlighting
        # Only needed if it differs from the 'name' field.
        'pygments_lexer': str,

        # Codemirror mode, for highlighting in the notebook.
        # Only needed if it differs from the 'name' field.
        'codemirror_mode': str or dict,

        # Nbconvert exporter, if notebooks written with this kernel should
        # be exported with something other than the general 'script'
        # exporter.
        'nbconvert_exporter': str,
    },

    # A banner of information about the kernel,
    # which may be desplayed in console environments.
    'banner': str,

    # A boolean flag which tells if the kernel supports debugging in the notebook.
    # Default is False
    'debugger': bool,

    # Optional: A list of dictionaries, each with keys 'text' and 'url'.
    # These will be displayed in the help menu in the notebook UI.
    'help_links': [
        {'text': str, 'url': str}
    ],
}