try to fix doc build

See merge request !321

.gitlab-ci.yml

@@ -4,6 +4,8 @@ image: sphinxdoc/sphinx
 before_script: []
 pages:
   script:
+    - pip3 install sphinx-autoapi
+    - pip3 install nbsphinx
     - sphinx-build -M html doc public
   artifacts:
     paths:

doc/conf.py

@@ -15,7 +15,6 @@
 import os
 import sys
 sys.path.insert(0, os.path.abspath('..'))
-import sphinx_rtd_theme
 
 # -- Project information -----------------------------------------------------
 
@@ -45,7 +44,6 @@ extensions = [
     'sphinx.ext.napoleon',
     'sphinx.ext.extlinks',
     'autoapi.extension',
-    'sphinx_rtd_theme',
     'nbsphinx'
 ]
 
@@ -98,8 +96,7 @@ pygments_style = None
 # The theme to use for HTML and HTML Help pages.  See the documentation for
 # a list of builtin themes.
 #
-#html_theme = 'alabaster'
-html_theme = 'sphinx_rtd_theme'
+html_theme = 'classic'
 
 # Theme options are theme-specific and customize the look and feel of a theme
 # further.  For a list of options available for each theme, see the