add arviz compat job

Author: MarcoGorelli

.github/workflows/arviz_compat.yml

@@ -0,0 +1,45 @@
+name: arviz-compatibility
+
+on:
+  pull_request:
+  push:
+    branches: [master]
+
+jobs:
+  pytest:
+    strategy:
+      matrix:
+        python-version: ["3.8"]
+        os: [ubuntu-18.04]
+        floatx: [float64]
+        test-subset:
+          - pymc3/tests/test_sampling.py
+    runs-on: ${{ matrix.os }}
+    env:
+      TEST_SUBSET: ${{ matrix.test-subset }}
+      THEANO_FLAGS: floatX=${{ matrix.floatx }},gcc.cxxflags='-march=native'
+    defaults:
+      run:
+        shell: bash -l {0}
+    steps:
+      - uses: actions/checkout@v2
+      - name: Cache conda
+        uses: actions/cache@v1
+        env:
+          # Increase this value to reset cache if environment-dev.yml has not changed
+          CACHE_NUMBER: 0
+        with:
+          path: ~/conda_pkgs_dir
+          key: ${{ runner.os }}-conda-${{ env.CACHE_NUMBER }}-${{
+            hashFiles('environment-dev.yml') }}
+      - uses: conda-incubator/setup-miniconda@v2
+        with:
+          activate-environment: testenv
+          channel-priority: strict
+          environment-file: environment-dev.yml
+          use-only-tar-bz2: true # IMPORTANT: This needs to be set for caching to work properly!
+      - run: |
+          conda activate testenv
+          conda remove arviz -y
+          pip install git+git://github.com/arviz-devs/arviz.git
+          python -m pytest -v --cov=pymc3 --cov-report=xml --cov-report term --durations=50 $TEST_SUBSET -n auto