python-poppler-0.12.1.ebuild says: RDEPEND="( >=app-text/poppler-0.12.3-r3[cairo] <app-text/poppler-0.16.0[cairo] ) pretty sure you want "||" in there
And you want to reverse the order. <app-text/poppler-0.16.0[cairo] will select a version that satisfies >=app-text/poppler-0.12.3-r3[cairo] too (if possible at all), while the reverse isn't true.
@vapier feel free to fix it, if you can.
looks like the 0.12.1 upgrade fixed things