Add copy button error:

[CodingCattwo]

Stacktrace:

Running Sphinx v1.6.7
...

Traceback (most recent call last):
  File "/home/docs/checkouts/readthedocs.org/user_builds/webase-doc-cattwo/envs/latest/lib/python3.7/site-packages/sphinx/cmdline.py", line 305, in main
    opts.warningiserror, opts.tags, opts.verbosity, opts.jobs)
  File "/home/docs/checkouts/readthedocs.org/user_builds/webase-doc-cattwo/envs/latest/lib/python3.7/site-packages/sphinx/application.py", line 196, in __init__
    self.setup_extension(extension)
  File "/home/docs/checkouts/readthedocs.org/user_builds/webase-doc-cattwo/envs/latest/lib/python3.7/site-packages/sphinx/application.py", line 456, in setup_extension
    self.registry.load_extension(self, extname)
  File "/home/docs/checkouts/readthedocs.org/user_builds/webase-doc-cattwo/envs/latest/lib/python3.7/site-packages/sphinx/registry.py", line 207, in load_extension
    metadata = mod.setup(app)
  File "/home/docs/checkouts/readthedocs.org/user_builds/webase-doc-cattwo/envs/latest/lib/python3.7/site-packages/sphinx_copybutton/__init__.py", line 25, in setup
    app.add_js_file('clipboard.min.js')
AttributeError: 'Sphinx' object has no attribute 'add_js_file'

Exception occurred:
  File "/home/docs/checkouts/readthedocs.org/user_builds/webase-doc-cattwo/envs/latest/lib/python3.7/site-packages/sphinx_copybutton/__init__.py", line 25, in setup
    app.add_js_file('clipboard.min.js')
AttributeError: 'Sphinx' object has no attribute 'add_js_file'

My doc project is WeBASE-Doc

[choldgraf]

@CodingCattwo can you upgrade sphinx and see if that fixes it?