WIP: skip doc build in test workflow for old spx.

Author: rossbar

.github/workflows/test.yml

@@ -13,7 +13,7 @@ jobs:
       matrix:
         os: [Ubuntu]
         python-version: [3.6, 3.7, 3.8, 3.9]
-        sphinx-version: ["sphinx==1.8.0", "sphinx==2.1", "sphinx>3.0"]
+        sphinx-version: ["sphinx==1.6.5", "sphinx==2.1", "sphinx>3.0"]
     steps:
     - uses: actions/checkout@v2
 
@@ -52,10 +52,12 @@ jobs:
         echo '! python -m numpydoc --validate numpydoc.tests.test_main._docstring_with_errors' | bash
 
     - name: Setup for doc build
+      if: ${{ matrix.sphinx-version }} != "sphinx==1.6.5"
       run: |
         sudo apt install texlive texlive-latex-extra latexmk dvipng
 
     - name: Build documentation
+      if: ${{ matrix.sphinx-version }} != "sphinx==1.6.5"
       run: |
         make -C doc html SPHINXOPTS="-nT"
         make -C doc latexpdf SPHINXOPTS="-nT"