Updating the More than one value stored for custom field id ERROR to a WARNING Message

In certain cases when older versions of JIRA (3.x) are upgraded to 4.x , during the reindexing process users may receive the following error:

012-10-18 15:37:32,757 issueIndexer:thread-2 ERROR user1 54467x282x1 116rbdw /secure/admin/jira/IndexReIndex.jspa [issue.customfields.impl.AbstractSingleFieldType] More than one value stored for custom field id 'customfield_10001' for issue 'DW-01'. Values [test , test ]

I've been told that this error message should really be a WARN in the log files as it should not affect JIRA performance.
Can we get this error message updated as there are many cases of this coming up. Currently the "workaround" is to manually delete database entries as proposed by https://jira.atlassian.com/browse/JRA-12796?focusedCommentId=88105&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-88105.

It would be nice for this to be included in the upgrade tasks as this is a common place where the issue seems to come up.