AttributeError: 'Sphinx' object has no attribute 'info'

[jiyun]

# Sphinx version: 2.2.1
# Python version: 3.6.8 (CPython)
# Docutils version: 0.15.2 release
# Jinja2 version: 2.10.3
# Last messages:

# Loaded extensions:
Traceback (most recent call last):
  File "/usr/local/lib64/python3.6/site-packages/sphinx/cmd/build.py", line 275, in build_main
    args.tags, args.verbosity, args.jobs, args.keep_going)
  File "/usr/local/lib64/python3.6/site-packages/sphinx/application.py", line 236, in __init__
    self.setup_extension(extension)
  File "/usr/local/lib64/python3.6/site-packages/sphinx/application.py", line 395, in setup_extension
    self.registry.load_extension(self, extname)
  File "/usr/local/lib64/python3.6/site-packages/sphinx/registry.py", line 487, in load_extension
    metadata = setup(app)
  File "/usr/local/lib/python3.6/site-packages/sphinxjp/themes/revealjs/__init__.py", line 26, in setup
    directives.setup(app)
  File "/usr/local/lib/python3.6/site-packages/sphinxjp/themes/revealjs/directives.py", line 315, in setup
    app.info('Initializing RevealJS theme directives')
AttributeError: 'Sphinx' object has no attribute 'info'