Add a note about the dependency between relative imports and the value in '__name__'

pep-0328.txt

@@ -267,6 +267,15 @@ is usable in an expression.  But ::
 is not usable in an expression.
 
 
+Relative Imports and __name__
+===============================
+
+Relative imports use a module's __name__ attribute to determine that
+module's position in the package hierarchy. If the module's name does
+not contain any package information (e.g. it is set to '__main__')
+then relative imports are resolved as if the module were a top level
+module, regardless of where the module is actually located on the file
+system.
 
 
 References