.github/workflows: Run tests on Debian buster i386.

In addition to running the test suite on the "latest" OS images
provided by GitHub, with the latest dependencies installed from pip,
also run the test suite on 32-bit Debian 10 (via Docker), with stable
dependencies installed from Debian.

This should help to catch incompatibilities with older package
versions, as well as errors due to differing CPU architectures.

Author: Benjamin Moody

.github/workflows/run-tests.yml

@@ -32,3 +32,29 @@ jobs:
       - name: Run nosetests
         run: |
           nosetests
+
+  test-deb10-i386:
+    runs-on: ubuntu-latest
+    container: i386/debian:10
+    steps:
+      - name: Install dependencies
+        run: |
+          apt-get update
+          apt-get install -y --no-install-recommends \
+                  python3-matplotlib \
+                  python3-numpy \
+                  python3-pandas \
+                  python3-requests \
+                  python3-scipy \
+                  python3-nose \
+                  git
+
+      # Note: "actions/checkout@v2" requires libstdc++6:amd64 to be
+      # installed in the container.  To keep things simple, use
+      # "actions/checkout@v1" instead.
+      # https://github.com/actions/checkout/issues/334
+      - uses: actions/checkout@v1
+
+      - name: Run nosetests
+        run: |
+          nosetests3