http 500, "unknown_error / funciton_clause authenticate_request"

[Chad Miller]

Binary package hint: couchdb

it caused HTTP 500 and couchdb described it as
{"error":"unknown_error","reason":"function_clause"}
{couch_httpd,authenticate_request,2},
             {couch_httpd,handle_request,5},
             {mochiweb_http,headers,5},
             {proc_lib,init_p_do_apply,3}