diff --git a/hacking/core.py b/hacking/core.py
index <HASH>..<HASH> 100644
--- a/hacking/core.py
+++ b/hacking/core.py
@@ -74,6 +74,10 @@ IMPORT_EXCEPTIONS += DEFAULT_IMPORT_EXCEPTIONS
 
 
 def is_import_exception(mod):
+    """Check module name to see if import has been whitelisted.
+
+       Import based rules should not run on any whitelisted module
+       """
     return (mod in IMPORT_EXCEPTIONS or
             any(mod.startswith(m + '.') for m in IMPORT_EXCEPTIONS))
Add docstring to is_import_exception

Clarify what is_import_exception does. Leave the name as
is_import_exception and no is_import_whitelisted  because
import-exceptions is part of the API for hacking (used in the hacking
section of tox.ini).

Change-Id: Ib<I>d<I>ecfcdbcb<I>b<I>ab<I>e<I>a<I>