Move import semantic util code to importlib.test.import_.util.

Lib/importlib/test/import_/util.py

@@ -0,0 +1,33 @@
+import functools
+import importlib
+
+
+using___import__ = False
+
+
+def import_(*args, **kwargs):
+    """Delegate to allow for injecting different implementations of import."""
+    if using___import__:
+        return __import__(*args, **kwargs)
+    return importlib.Import()(*args, **kwargs)
+
+
+def importlib_only(fxn):
+    """Decorator to mark which tests are not supported by the current
+    implementation of __import__()."""
+    def inner(*args, **kwargs):
+        if using___import__:
+            return
+        else:
+            return fxn(*args, **kwargs)
+    functools.update_wrapper(inner, fxn)
+    return inner
+
+
+def mock_path_hook(*entries, importer):
+    """A mock sys.path_hooks entry."""
+    def hook(entry):
+        if entry not in entries:
+            raise ImportError
+        return importer
+    return hook