CI: Prettify gradient check output

Make the result more informative and more readable.

tests/benchmark-models/test_petab_benchmark.py

@@ -19,6 +19,7 @@
 from fiddy.extensions.amici import simulate_petab_to_cached_functions
 from fiddy.success import Consistency
 
+
 repo_root = Path(__file__).parent.parent.parent
 
 # reuse compiled models from test_benchmark_collection.sh
@@ -110,7 +111,11 @@ def assert_gradient_check_success(
     if check_result.success is True:
         return
 
-    raise AssertionError(f"Gradient check failed:\n{check_result.df}")
+    df = check_result.df
+    df["abs_diff"] = np.abs(df["expectation"] - df["test"])
+    df["rel_diff"] = df["abs_diff"] / np.abs(df["expectation"])
+    with pd.option_context("display.max_columns", None, "display.width", None):
+        raise AssertionError(f"Gradient check failed:\n{df}")
 
 
 @pytest.mark.filterwarnings(
@@ -201,7 +206,6 @@ def test_benchmark_gradient(model, scale, sensitivity_method, request):
         # cache=not debug,
         cache=False,
     )
-
     noise_level = 0.1
     np.random.seed(cur_settings.rng_seed)