Add i386: Intel 32-bit case to Travis CI

.travis.yml

@@ -4,6 +4,19 @@ python:
   - "3.7"
   - "3.6"  
   - "3.8-dev"
+matrix:
+  include:
+    # i386: Intel 32-bit
+    - name: i386
+      language: minimal
+      install: |
+        docker run --rm --privileged multiarch/qemu-user-static --reset -p yes &&
+          docker build --rm --build-arg BASE_IMAGE="i386/ubuntu:bionic" -t macs -f test/Dockerfile .
+      script: |
+        docker run --rm -t macs bash -cx "pytest --runxfail && cd test && ./cmdlinetest macs2"
+  allow_failures:
+    - name: i386
+  fast_finish: true
 install:
   - pip install --upgrade pip
   - pip install --upgrade -r requirements.txt

test/Dockerfile

@@ -0,0 +1,29 @@
+ARG BASE_IMAGE=ubuntu:bionic
+FROM ${BASE_IMAGE}
+
+ENV TEST_USER macs
+
+RUN uname -a
+RUN apt-get update -qq && \
+  apt-get install -yq \
+  python3 \
+  python3-pip \
+  python3-setuptools \
+  python3-wheel
+
+RUN useradd -m "${TEST_USER}"
+WORKDIR /build
+COPY . .
+RUN chown -R "${TEST_USER}:${TEST_USER}" /build
+
+USER "${TEST_USER}"
+RUN env | grep ^PATH
+ENV PATH "/home/${TEST_USER}/.local/bin:${PATH}"
+
+RUN python3 --version
+RUN pip3 --version
+
+RUN pip3 install --user --upgrade -r requirements.txt
+RUN pip3 install --user .
+
+RUN pytest --version