Export constants from ``.base``

Used by other modules; these exports got removed when I replaced an ``import *`` earlier.

NEWS.rst

@@ -2,6 +2,9 @@
 History
 *******
 
+Export constants from ``.base``.
+Used by other modules; these exports got removed when I replaced an ``import *`` earlier.
+
 13.0.3.1.0
 ==========
 

__init__.py

@@ -20,6 +20,11 @@
 
 from . import models
 from .base import (
+    OPERATION_CREATION,
+    OPERATION_UPDATE,
+    PHASE_POSTCREATE,
+    PHASE_PRECREATE,
+    PHASE_UPDATE,
     Computed,
     Constant,
     ContextBuilder,