Show returncode when subprocess test fails

timhoffm · timhoffm · commit 240ea856da06 · 2019-01-15T22:33:06.000+01:00
diff --git a/lib/matplotlib/tests/test_backends_interactive.py b/lib/matplotlib/tests/test_backends_interactive.py
@@ -110,10 +110,12 @@ def check_alt_backend(alt_backend):
 @pytest.mark.parametrize("backend", _get_testable_interactive_backends())
 @pytest.mark.flaky(reruns=3)
 def test_interactive_backend(backend):
-    if subprocess.run([sys.executable, "-c", _test_script],
-                      env={**os.environ, "MPLBACKEND": backend},
-                      timeout=_test_timeout).returncode:
-        pytest.fail("The subprocess returned an error.")
+    proc = subprocess.run([sys.executable, "-c", _test_script],
+                          env={**os.environ, "MPLBACKEND": backend},
+                          timeout=_test_timeout)
+    if proc.returncode:
+        pytest.fail("The subprocess returned with non-zero exit status "
+                    f"{proc.returncode}.")
 
 
 @pytest.mark.skipif('SYSTEM_TEAMFOUNDATIONCOLLECTIONURI' in os.environ,
