When I generate the DITA XML output and then open the dita map in Oxygen, the map is invalid.  The file names generated by the DITA XML output type, contain spaces so I get these types of errors for every topicref or mapref in my ditamap:

Reference "Testing outputclass settings for task labels=GUID-8098B536-DC76-49A7-B9D9-91A111FEA714=2=en-US=.xml" contains characters which are not properly URI-encoded, it should be replaced with "Testing%20outputclass%20settings%20for%20task%20labels=GUID-8098B536-DC76-49A7-B9D9-91A111FEA714=2=en-US=.xml".

How do I change the file names generated by the DITA XML output type to not contain spaces?