Restore testing on 3.6

.github/workflows/R-CMD-check.yml

@@ -48,7 +48,7 @@ jobs:
         config:
           - {os: windows-latest, r: 'release'}
           - {os: macOS-latest, r: 'release'}
-          - {os: ubuntu-latest, r: '4.1', rspm: "https://packagemanager.rstudio.com/cran/__linux__/focal/latest"}
+          - {os: ubuntu-latest, r: '3.6', rspm: "https://packagemanager.rstudio.com/cran/__linux__/focal/latest"}
           - {os: ubuntu-latest, r: 'release', rspm: "https://packagemanager.rstudio.com/cran/__linux__/focal/latest"}
           - {os: ubuntu-latest, r: 'devel', rspm: "https://packagemanager.rstudio.com/cran/__linux__/focal/latest"}
 
@@ -78,7 +78,21 @@ jobs:
         run: |
           sudo apt-get update
           sudo apt-get install -y texlive-latex-base libglpk-dev texlive-fonts-recommended
-                      
+
+      - name: Set up R dependencies (R 3.6)
+        if: matrix.config.r == '3.6'
+        uses: r-lib/actions/setup-r-dependencies@v2
+        with:
+          extra-packages: |
+            [email protected]
+            [email protected]
+            [email protected]
+            [email protected]
+            [email protected]
+            [email protected]
+          needs: |
+            check
+
       - name: Set up R dependencies (Windows)
         if: runner.os == 'Windows'
         uses: r-lib/actions/setup-r-dependencies@v2
@@ -92,7 +106,7 @@ jobs:
             coverage
             
       - name: Set up R dependencies (Non-Windows)
-        if: runner.os != 'Windows'
+        if: runner.os != 'Windows' && matrix.config.r != '3.6'
         uses: r-lib/actions/setup-r-dependencies@v2
         with:
           extra-packages: |