Added a warning message in case a file could not be cleaned up.
Added a warning message in case a file could not be cleaned up.

If a file was created but the database reference fails, the file is cleaned up. But, if it failed to clean up the file, it was silently ignored. Now, a warning message is output.

Closes #366

HaiJiaoXinHeng/server-1,HaiJiaoXinHeng/server-1,HaiJiaoXinHeng/server-1,hongsudt/server,hongsudt/server,hongsudt/server