"Could not fetch page info" should not look like a content linting error

[wbamberg]

When we run the linter and it can't fetch some pages (which often happens when running it over all the JS pages) it logs this as a content error:

Expected SpecName macro for data.specifications                                                                                                            2 errors       javascript-constructor/data.specifications/expected-macro 
Could not fetch page info from https://wiki.developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/is$json (504 GATEWAY_TIMEOUT)  2 errors       null                                                      
Macro: anch                                                                                                                                                2 warnings     anch                                                      
Macro: Next                                                                                                                                                1 warning      next                              

There are a couple of problems with this:

• it's not correct to say this is a content error
• the message is so long that it often breaks the layout of the report.

It would be better if we could log this in a separate section:

Could not lint the following pages:
https://wiki.developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/is$json (504 GATEWAY_TIMEOUT)