We need this file otherwise we get an error from sphinx (autoapi) like this:

...
...
[AutoAPI] Ignoring /km3pipe/km3modules/tests/test_common.py
[AutoAPI] Ignoring /km3pipe/km3modules/tests/test_mc.py
[AutoAPI] Reading files... [100%] /km3pipe/km3modules/hardware.py
/usr/local/lib/python3.6/site-packages/autoapi/extension.py:96: RemovedInSphinx20Warning: app.info() is now deprecated. Use sphinx.util.logging instead.
  app.info(bold('[AutoAPI] ') + darkgreen('Mapping Data'))
[AutoAPI] Mapping Data

Exception occurred:
  File "/usr/local/lib/python3.6/site-packages/sphinx_gallery/gen_gallery.py", line 257, in touch_empty_backreferences
    open(examples_path, 'w').close()
FileNotFoundError: [Errno 2] No such file or directory: '/km3pipe/doc/modules/generated/km3pipe.calib.examples'
The full traceback has been saved in /tmp/sphinx-err-_i42cm23.log, if you want to report the issue to the developers.
Please also report this if it was a user error, so that a better error message can be provided next time.
A bug report can be filed in the tracker at <https://github.com/sphinx-doc/sphinx/issues>. Thanks!
Makefile:62: recipe for target 'html' failed
make: *** [html] Error 2
