Improve the GitHub test phase.

I incorporated the changes in tox.ini into the automated test workflow
so that we do not end up tagging a broken build :/

.github/workflows/run-tests.yml

@@ -21,15 +21,21 @@ jobs:
           python-version: ${{ matrix.python-version }}
       - name: Install dependencies
         run: |
-          python -m pip install --upgrade pip setuptools
+          python -m pip install --upgrade pip setuptools twine wheel
           python -m pip install '.[dev]'
           python -m pip install -e .
       - name: Lint
         run: |
-          flake8 sprockets_statsd tests
+          flake8 sprockets_statsd tests setup.py docs/conf.py
       - name: Check format
         run: |
-          yapf -dr sprockets_statsd tests
+          yapf -dr sprockets_statsd tests setup.py docs/conf.py
+      - name: Verify distribution build
+        run: |
+          rm -fr dist
+          python setup.py bdist_wheel
+          python setup.py sdist
+          twine check dist/*
       - name: Run tests
         run: |
           coverage run -m unittest