bpo-32872: Avoid regrtest compatibility issue with namespace packages. (GH-6276)

diff --git a/Lib/test/libregrtest/setup.py b/Lib/test/libregrtest/setup.py
index bf899a9..910aca1 100644
--- a/Lib/test/libregrtest/setup.py
+++ b/Lib/test/libregrtest/setup.py
@@ -57,7 +57,7 @@
         if hasattr(module, '__path__'):
             for index, path in enumerate(module.__path__):
                 module.__path__[index] = os.path.abspath(path)
-        if hasattr(module, '__file__'):
+        if getattr(module, '__file__', None):
             module.__file__ = os.path.abspath(module.__file__)
 
     # MacOSX (a.k.a. Darwin) has a default stack size that is too small