Update README on how to run tests after migrations

README.rst

@@ -124,6 +124,10 @@ Tests
 
     py.test --cov . --cov-report term --cov-report html && firefox htmlcov/index.html
 
+* The first time you run the tests after a migration (``./manage.py migrate``) use the db recreation option.
+  This needs to be done only once::
+
+    py.test --create-db
 
 Issues
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