When dealing with __import__ for detecting a global state change made by a
test, make sure to check if __builtins__ is a dict or not.

Discovered when running importlib.test.regrtest.
diff --git a/Lib/test/regrtest.py b/Lib/test/regrtest.py
index 34b743e..8b46f6e 100755
--- a/Lib/test/regrtest.py
+++ b/Lib/test/regrtest.py
@@ -859,9 +859,15 @@
         sys.path_hooks[:] = saved_hooks[2]
 
     def get___import__(self):
-        return __builtins__.__import__
+        if isinstance(__builtins__, dict):
+            return __builtins__['__import__']
+        else:
+            return __builtins__.__import__
     def restore___import__(self, import_):
-        __builtins__.__import__ = import_
+        if isinstance(__builtins__, dict):
+            __builtins__['__import__'] = import_
+        else:
+            __builtins__.__import__ = import_
 
     def get_warnings_filters(self):
         return id(warnings.filters), warnings.filters, warnings.filters[:]