Question: During what season of Europe's secondary club football tournament was the  2017 UEFA Europa League Final, where Manchester United finished in sixth place?

Context articles: 2016–17 Manchester United F.C. season
2014 UEFA Europa League Final
2019 UEFA Europa League Final
2013 UEFA Europa League Final
2017 UEFA Europa League Final
2016 UEFA Europa League Final
2011 UEFA Europa League Final
2012 UEFA Europa League Final
2018 UEFA Europa League Final
2015 UEFA Europa League Final

The 2016–17 season was Manchester United's 25th season in the Premier League, and their 42nd consecutive season in the top-flight of English football.
 It began against Leicester City in the FA Community Shield, with United prevailing 2–1 to win the first trophy of the domestic calendar.
 In February 2017, the club won their second trophy of the campaign, beating Southampton 3–2 in the EFL Cup Final.
 Although they missed out on qualifying for the 2017–18 UEFA Champions League via the league, having finished in sixth place, a 2–0 victory over Ajax in the 2017 UEFA Europa League Final meant they qualified for the Champions League group stage as Europa League title holders.
The 2014 UEFA Europa League Final was the final match of the 2013–14 UEFA Europa League, the 43rd season of Europe's secondary club football tournament organised by UEFA, and the fifth season since it was renamed from the UEFA Cup to the UEFA Europa League.
 It was played at the Juventus Stadium in Turin, Italy on 14 May 2014, between Spanish side Sevilla and Portuguese side Benfica.
 Sevilla won the match 4–2 on penalties, following a 0–0 draw after extra time.
The 2019 UEFA Europa League Final will be the final match of the 2018–19 UEFA Europa League, the 48th season of Europe's secondary club football tournament organised by UEFA, and the 10th season since it was renamed from the UEFA Cup to the UEFA Europa League.
 It will be played at the Olympic Stadium in Baku, Azerbaijan on 29 May 2019.
 Starting from this season, the Europa League final will be played in the same week as the Champions League final.
The 2013 UEFA Europa League Final was the final match of the 2012–13 UEFA Europa League, the 42nd season of Europe's secondary club football tournament organised by UEFA, and the 4th season since it was renamed from the UEFA Cup to the UEFA Europa League.
 The match was played at the Amsterdam Arena in Amsterdam, the Netherlands, on 15 May 2013, between Portuguese side Benfica and English side Chelsea.
 Chelsea won 2–1 to secure their first title in this competition.
The 2017 UEFA Europa League Final was the final match of the 2016–17 UEFA Europa League, the 46th season of Europe's secondary club football tournament organised by UEFA, and the 8th season since it was renamed from the UEFA Cup to the UEFA Europa League.
 It was played at the Friends Arena in Solna, Sweden on 24 May 2017, between Dutch side Ajax and English side Manchester United.
 Manchester United won the match 2–0 to secure their first title in this competition.
 With this victory, they joined Juventus, Ajax, Bayern Munich and Chelsea as the only clubs to have won all three major European trophies (European Champion Clubs' Cup/UEFA Champions League, UEFA Cup/Europa League, and the now defunct UEFA Cup Winners' Cup).
The 2016 UEFA Europa League Final was the final match of the 2015–16 UEFA Europa League, the 45th season of Europe's secondary club football tournament organised by UEFA, and the seventh season since it was renamed from the UEFA Cup to the UEFA Europa League.
 It was played at the St. Jakob-Park in Basel, Switzerland on 18 May 2016, between English team Liverpool and Spanish team and two-time defending champions Sevilla.
 Sevilla won the match 3–1 to become the first team to win the UEFA Cup/Europa League three times in a row; it was their record fifth title overall.
The 2011 UEFA Europa League Final was the final match of the 2010–11 UEFA Europa League, the 40th season of Europe's secondary club football tournament organised by UEFA, and the second season since it was renamed from UEFA Cup to UEFA Europa League.
 The match was played at the Aviva Stadium in Dublin, Republic of Ireland, on 18 May 2011, between two Portuguese teams – Porto and Braga – for the first time in UEFA competition finals.
The 2012 UEFA Europa League Final was the final match of the 2011–12 UEFA Europa League, the 41st season of Europe's secondary club football tournament organised by UEFA (after the UEFA Champions League), and the 3rd season since it was renamed from the UEFA Cup to the UEFA Europa League.
 The match was played on 9 May 2012 at the Arena Națională in Bucharest, Romania, and was contested between two Spanish sides – Atlético Madrid and Athletic Bilbao.
 The match ended with Atlético Madrid winning 3–0, with Radamel Falcao scoring two goals and Diego scoring another.
 In doing so, Falcao was named man of the match, and became the first player to win back-to-back Europa League titles with different teams.
The 2018 UEFA Europa League Final will be the final match of the 2017–18 UEFA Europa League, the 47th season of Europe's secondary club football tournament organised by UEFA, and the 9th season since it was renamed from the UEFA Cup to the UEFA Europa League.
 It will be played at the Parc Olympique Lyonnais in Décines-Charpieu, France on 16 May 2018.
The 2015 UEFA Europa League Final was the final match of the 2014–15 UEFA Europa League, the 44th season of Europe's secondary club football tournament organised by UEFA, and the sixth season since it was renamed from the UEFA Cup to the UEFA Europa League.
 It was played at the National Stadium in Warsaw, Poland, on 27 May 2015, between Ukrainian side Dnipro Dnipropetrovsk and the title holders, Spanish side Sevilla.
 Sevilla won the match 3–2 for a record fourth title.