ihooks FancyModuleLoader.load_module()
imputils Importer._process_result():
    remove name from modules dict if exec fails.

This is what all the builtin importers do now, new in 2.4.
diff --git a/Lib/imputil.py b/Lib/imputil.py
index 04111dc..e6ad7ec 100644
--- a/Lib/imputil.py
+++ b/Lib/imputil.py
@@ -297,7 +297,12 @@
 
         # execute the code within the module's namespace
         if not is_module:
-            exec code in module.__dict__
+            try:
+                exec code in module.__dict__
+            except:
+                if fqname in sys.modules:
+                    del sys.modules[fqname]
+                raise
 
         # fetch from sys.modules instead of returning module directly.
         # also make module's __name__ agree with fqname, in case