add a helpful response to SearchIndexError exceptions raised within the action api
[#835] return str(exception) on SearchIndexError in acton API
Merge branch '835-helpful-action-api-search-index-error' of git://github.com/open-data/ckan into open-data-835-helpful-action-api-search-index-error
Merge branch 'open-data-835-helpful-action-api-search-index-error'