xbps-bin: improve error printfs while checking files.plist.
xbps-bin: improve error printfs while checking files.plist.

datenwolf/xbps,stpx/xbps,ebfe/xbps,stpx/xbps,datenwolf/xbps,ebfe/xbps,ebfe/xbps,datenwolf/xbps,stpx/xbps