Maltese Prime Minister Joseph Muscat (L), Hungary's Prime Minister Victor Orban (2nd L), Germany's Chancellor Angela Merkel and Austria's Chancellor Christian Kern (R) arrive to pose for a family photo during the European Union summit- the first one since Britain voted to quit- in Bratislava, Slovakia, September 16, 2016. REUTERS/Leonhard Foeger

Hungary's Prime Minister Victor Orban arrives to pose for a family photo during the European Union summit- the first one since Britain voted to quit- in Bratislava, Slovakia, September 16, 2016. REUTERS/Leonhard Foeger

Greece's Prime Minister Alexis Tsipras (C), Germany's Chancellor Angela Merkel and Portugal's Prime Minister Antonio Costa (R) arrive to pose for a family photo during the European Union summit- the first one since Britain voted to quit- in Bratislava, Slovakia, September 16, 2016. REUTERS/Leonhard Foeger

California Governor Jerry Brown leaves the stage at the Democratic National Convention in Philadelphia, Pennsylvania, U.S. July 27, 2016. REUTERS/Scott Audette

Hungarian Prime Minister Viktor Orban delivers a speech during a business conference in Budapest, Hungary, March 10, 2016. REUTERS/Laszlo Balogh

Britain Tennis - Great Britain v Argentina - Davis Cup Semi Final - Emirates Arena, Glasgow, Scotland - 16/9/16 Great Britain's Andy Murray after losing his match against Argentina's Juan Martin del Potro Action Images via Reuters / Andrew Boyers Livepic

Britain Tennis - Great Britain v Argentina - Davis Cup Semi Final - Emirates Arena, Glasgow, Scotland - 16/9/16 Great Britain's Andy Murray looks dejected during his match against Argentina's Juan Martin del Potro Action Images via Reuters / Andrew Boyers Livepic

Britain Tennis - Great Britain v Argentina - Davis Cup Semi Final - Emirates Arena, Glasgow, Scotland - 16/9/16 Argentina's Juan Martin del Potro in action against Great Britain's Andy Murray Action Images via Reuters / Andrew Boyers Livepic