editorial fix

docs/userguide/package_discovery.rst

@@ -90,7 +90,7 @@ in ``src`` that starts with the name ``pkg`` and not ``additional``:
         packages = find_packages(
             where = 'src',
             include = ['pkg*',],
-            exclude = ['tests',]
+            exclude = ['additional',]
         ),
         package_dir = {"":"src"}
         #...