PR#2342: fix simple_error_message encoding
    
    Merges #2342
    https://pagure.io/koji/pull-request/2342
    
    Fixes: #1977
    https://pagure.io/koji/issue/1977
    koji-web should log an error if it cannot read /etc/kojiweb/web.conf
    
    Fixes: #2341
    https://pagure.io/koji/issue/2341
    web: simple_error_message has wrong encoding for py3