gha: publish: don't forget gpg

.github/workflows/pythonpublish.yml

@@ -30,10 +30,19 @@ jobs:
       uses: actions/setup-python@v2
       with:
         python-version: ${{ matrix.python-version }}
+    - name: Install native dependencies (Ubuntu)
+      run: sudo apt-get update && sudo apt-get install -y libgpgme-dev libgpg-error-dev
+      if: "matrix.os == 'ubuntu-latest'"
+    - name: Install native dependencies (MacOS)
+      run: brew install swig gpgme
+      if: "matrix.os == 'macos-latest'"
     - name: Install dependencies
       run: |
         python -m pip install --upgrade pip
         pip install setuptools wheel twine fastimport
+    - name: Install gpg on supported platforms
+      run: pip install -U gpg
+      if: "matrix.os != 'windows-latest' && matrix.python-version != 'pypy3'"
     - name: Run test suite
       run: |
         python -m unittest dulwich.tests.test_suite