#436 wrong highlighting and replace with code with syntax errors

[Patrick Gerken]

If you edit a python file, and add something that breaks the code in such a way that it does not compile, the yellow highlighting highlights old places and the refactoring breaks.
If the file is bigger then one screensize one can oversee the error. Instead, it would be better, thet the functionality is turned of, if the code can't be parsed.

The red error marker on the left side of the editor is not always enough of a warning, I have often plenty of them, because I edit code that has some magic that extends my global namespace, and uses libraries not available on the machine I am working on.