submission parser should provide essential diagnostic on partial submissions

[Zygmunt Krynicki]

After spending a few days tracking bugs related to "empty submissions" and fixing several related bugs to bring back the submission parser and everything else required to parse stuff from both the certification website and checkbox's sides of the stack I think that we need a lot better diagnostic that is clearly identifying broken submissions that would result in a typical empty submission page:

For reference: https://code.launchpad.net/~zkrynicki/checkbox/fix-1312808/+merge/219850