Hey, I built the latest SDL2 development version from mercurial (in 64-bit Linux), only to find out that my spacebar presses are not being registered in an SDL2 app, while all the other keys are working fine.
Since this looks like an important issue, I was instructed to post it here.
Using hg bisect, I was able to track down the changeset that caused the issue: 9842:8a89b58895c1 (http://hg.libsdl.org/SDL/rev/8a89b58895c1 - “Supply current group when translating X11 Keycodes to Keysyms.”)
I have submitted a bug report for the issue at https://bugzilla.libsdl.org/show_bug.cgi?id=3130