Issue #2142999 by stefan.r, fago: Test for EntityTypeConstraintValidator.
Issue #2093477 by Tor Arne Thune: Terse text for setting theme as default on Appearance page.
Issue #2152225 by longwave, JeroenT, steveoliver, joelpittet, hussainweb, shanethehat, jenlampton, kpa, AnythonyR, EVIIILJ, kgoel, Cottser, dsdeiz, hanpersand: Convert theme_select() to Twig
Issue #1982776 by netsensei, Dave Reid, plopesc: Formatters do not support weights like widgets do.