These three tags all refer to the same concept, with the slight exception of filenotfoundexception.
While we would usually merge the two smaller tags into the bigger tag, I feel that filenotfound and filenotfoundexception should be merged into file-not-found in order to relieve any confusion for new users.
The filenotfoundexception tag gives off the impression that it is for languages that actually have a
FileNotFoundException. This may confuse users and may have been the reason for the creation of the filenotfound and file-not-found tags.
Ergo, we should merge filenotfound and filenotfoundexception into file-not-found and also transfer the wiki from filenotfoundexception to file-not-found. Make sure that if the wiki is transferred that we remove all references to exceptions.