[PATCH 0 of 3] Fix rst syntax errors translation and test it

[Simon Heimberg]

Some more entries are probably formatted wrong, but this does not block 
generating the documentation.

Fixing the test does prevent to reintroduce such errors. The test still 
passes and does really check what it should (issue4003).

Patch 3 would trigger when a wrong language variable would be used again or 
when there would be a typo in a language short name ("De" instead of "de").