vterm: Use errno.EWOULDBLOCK instead of 11.
vterm: Use errno.EWOULDBLOCK instead of 11.

This will fix issues with unit tests on FreeBSD and hopefully on Mac OS
X, too.

douglas-larocca/urwid,urwid/urwid,Julian/urwid,mountainstorm/urwid,foreni-packages/urwid,zyga/urwid,westurner/urwid,foreni-packages/urwid,rndusr/urwid,inducer/urwid,westurner/urwid,harlowja/urwid,ivanov/urwid,harlowja/urwid,bk2204/urwid,wardi/urwid,inducer/urwid,hkoof/urwid,drestebon/urwid,Julian/urwid,tonycpsu/urwid,ivanov/urwid,inducer/urwid,drestebon/urwid,drestebon/urwid,foreni-packages/urwid,tonycpsu/urwid,wardi/urwid,westurner/urwid,ivanov/urwid,douglas-larocca/urwid,Julian/urwid,mountainstorm/urwid,harlowja/urwid,rndusr/urwid,urwid/urwid,mountainstorm/urwid,douglas-larocca/urwid,hkoof/urwid,wardi/urwid,bk2204/urwid,tonycpsu/urwid,bk2204/urwid,urwid/urwid,rndusr/urwid,zyga/urwid,zyga/urwid,hkoof/urwid