A Kurdish woman holds a photo of the jailed co-leader of the opposition pro-Kurdish Peoples' Democratic Party (HDP), Selahattin Demirtas, during a rally of the HDP on the eve of the constitutional referendum, on April 15, 2017 in Diyarbakir.

The April 16 referendum will take place under a state of emergency that has been in place since last summer's failed coup, which has seen some 47,000 arrested in the biggest crackdown in Turkey's history. / AFP PHOTO / ILYAS AKENGIN        (Photo credit should read ILYAS AKENGIN/AFP/Getty Images)