Add test with lowest supported Pandas version

.github/workflows/build.yml

@@ -36,6 +36,13 @@ jobs:
         if: ${{ matrix.python-version }}=="3.9"
         run: |
           pip uninstall -y pyarrow vegafusion vegafusion-python-embed
+      - name: Maybe install lowest supported Pandas version
+        # We install the lowest supported Pandas version for one job to test that
+        # it still works. We do this for Python 3.8 as that is the last Python version
+        # to work with this Pandas version.
+        if: ${{ matrix.python-version }}=="3.8"
+        run: |
+          pip install pandas==0.18
       - name: Test that schema generation has no effect
         run: |
           python tools/generate_schema_wrapper.py

pyproject.toml

@@ -18,8 +18,10 @@ authors = [ {name = "Vega-Altair Contributors"} ]
 dependencies = [
     "typing_extensions>=4.0.1; python_version<\"3.11\"",
     "jinja2",
+    # If you update the minimum required jsonschema version, also update it in build.yml
     "jsonschema>=3.0",
     "numpy",
+    # If you update the minimum required pandas version, also update it in build.yml
     "pandas>=0.18",
     "toolz"
 ]