Catch editor exiting with nonzero status

Review Request #6843 — Created Jan. 31, 2015 and discarded — Latest diff uploaded

Information

RBTools
master

Reviewers

Now edit_text doesn't try and read the temp file if the editor launches, but
exits with a nonzero status code.

I need a hand here, it looks like edit_text is only called from merge, and I'm not sure how rbt merge works.

This should not ship till I test this.