Add a black format check

.github/workflows/tests.yml

@@ -20,7 +20,7 @@ concurrency:
 
 jobs:
   clang-format:
-    name: Formatting Check
+    name: C++ Formatting Check
     runs-on: ubuntu-latest
     strategy:
       matrix:
@@ -35,6 +35,15 @@ jobs:
         with:
           clang-format-version: "17"
           check-path: ${{ matrix.path }}
+  black:
+    name: Python Formatting Check
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: psf/black@stable
+        with:
+          options: "--check -v"
+          src: "python/neml2_wrap tests/python"
   copyright:
     name: Copyright check
     runs-on: ubuntu-latest