DOC: Pin sphinx to 1.8.5 (#26781)

Author: jorisvandenbossche

ci/deps/travis-36-doc.yaml

@@ -33,8 +33,8 @@ dependencies:
   - pytz
   - scipy
   - seaborn
-  # recursion error with sphinx 2.1.0. https://github.com/pandas-dev/pandas/issues/26723
-  - sphinx==2.0.1
+  # some styling is broken with sphinx >= 2 (https://github.com/pandas-dev/pandas/issues/26058)
+  - sphinx=1.8.5
   - sqlalchemy
   - statsmodels
   - xarray

environment.yml

@@ -26,7 +26,8 @@ dependencies:
 
   # documentation
   - gitpython  # obtain contributors from git for whatsnew
-  - sphinx
+  # some styling is broken with sphinx >= 2 (https://github.com/pandas-dev/pandas/issues/26058)
+  - sphinx=1.8.5
   - numpydoc>=0.9.0
 
   # documentation (jupyter notebooks)

requirements-dev.txt

@@ -11,7 +11,7 @@ isort
 mypy
 pycodestyle
 gitpython
-sphinx
+sphinx==1.8.5
 numpydoc>=0.9.0
 nbconvert>=5.4.1
 nbsphinx