Add test_env.py and test_writer_error.py for error handling patch (#7980)

Author: iloveme81189-del

test_env.py

@@ -0,0 +1,3 @@
+import torch, monai
+print("Torch version:", torch.__version__)
+print("MONAI version:", monai.__version__)

test_writer_error.py

@@ -0,0 +1,18 @@
+from monai.data.image_writer import resolve_writer, OptionalImportError, SUPPORTED_WRITERS, EXT_WILDCARD, ITKWriter
+
+ext = "fakeext"
+
+print(f"Before clearing fallback writers: {SUPPORTED_WRITERS.get(EXT_WILDCARD)}")
+
+# Temporarily clear fallback writers to simulate no support
+SUPPORTED_WRITERS[EXT_WILDCARD] = ()
+
+try:
+    writers = resolve_writer(ext, error_if_not_found=True)
+except OptionalImportError as e:
+    print("Caught OptionalImportError:", e)
+finally:
+    # Restore the fallback writers to avoid side effects
+    SUPPORTED_WRITERS[EXT_WILDCARD] = (ITKWriter,)
+
+print(f"After restoring fallback writers: {SUPPORTED_WRITERS.get(EXT_WILDCARD)}")