TST: Validate the return code of test_full_reimport

All errors raised within the sub process will remain silenced if the return code isn't validated

Author: BvB93

numpy/tests/test_reloading.py

@@ -57,5 +57,8 @@ def test_full_reimport():
         with warns(UserWarning):
             import numpy as np
         """)
-    p = subprocess.run([sys.executable, '-c', code])
-
+    p = subprocess.run([sys.executable, '-c', code], capture_output=True)
+    if p.returncode:
+        raise AssertionError(
+            f"Non-zero return code: {p.returncode!r}\n\n{p.stderr.decode()}"
+        )