Question: What nationality is the Sauber Formula One racer who drove the C34 in the 2015 season?

Context articles: Ruth Buscombe
Sauber C34
Marcus Ericsson
Sauber C12
Esteban Gutiérrez
Sauber C18
Sauber C19
Sauber C20
Sauber C17
Sauber C16

Ruth Buscombe is a British strategy engineer for the Sauber Formula One team.
 A first class honours graduate of the University of Cambridge Department of Engineering, she began working in Formula One with Scuderia Ferrari at the team's headquarters in 2012 as a race strategist, and later moved to Haas in November 2015.
 Buscombe operated as the team's strategy engineer and helped them achieve a strong start to the 2016 season.
 She left in June and was employed by Sauber three months later, helping the team to finish ahead of Manor Racing in the Constructors' Championship.
 Buscombe is an ambassador for Dare to be Different.
The Sauber C34 is a Formula One racing car which Sauber used to compete in the 2015 Formula One season.
 The C34 was driven by Marcus Ericsson and Felipe Nasr.
Marcus Ericsson (born 2 September 1990) is a Swedish race car driver currently racing for Sauber in Formula One, where he is contracted to the end of the 2017 season.
The Sauber C12 was the car with which the Sauber Formula One team made its FIA Formula One World Championship debut in 1993.
 Its design was led by Leo Ress.
 Power was provided by a Sauber-branded 3.5-litre V10 built by Ilmor in partnership with Mercedes.
 The C12 was given the prominence of "Concept by Mercedes-Benz" stickers on the engine cowling due to the two parties' close relationship from their World Sportscar Championship program.
 Indeed, the engines were re-branded in 1994 to reflect the partnership.
Esteban Manuel Gutiérrez Gutiérrez (] ; born 5 August 1991), is a Mexican racing driver.
 From 2011 to 2014, Gutiérrez drove for the Sauber Formula One team but lost his drive at the end of the 2014 season.
 He then signed with Ferrari as their test and reserve driver for 2015.
 Gutiérrez drove for the Haas F1 Team for the 2016 Formula One season.
The Sauber C18 was the car with which the Sauber Formula One team competed in the 1999 Formula One season.
 It was driven by Jean Alesi, in his second year with the team, and Pedro Diniz, who replaced Stewart-bound Johnny Herbert.
The Sauber C19 was the car with which the Sauber Formula One team competed in the 2000 Formula One season.
 It was driven by the experienced pairing of Mika Salo and Pedro Diniz, who had previously been team mates at Arrows in 1998.
The Sauber C20 was the car with which the Sauber Formula One team competed in the 2001 Formula One season.
 It was powered by a Petronas-branded '01A' 3.0-litre V10, supplied by Scuderia Ferrari.
 The C20 was notable not only for its eventual position in the Constructors' World Championship but also for a new type of front suspension mounting: the "twin keel".
The Sauber C17 was the car with which the Sauber Formula One team competed in the 1998 Formula One season.
 It was driven by Jean Alesi, who joined from Benetton, and Johnny Herbert, who was in his third season with the team after an impressive 1997 season.
The Sauber C16 was the car with which the Sauber Formula One team competed in the 1997 Formula One season.
 It was initially driven by Johnny Herbert, who was in his second season with the team, and Nicola Larini.
 Larini's place in the team was secured via an arrangement that gave the team the previous year's Ferrari engines that were used in the F310 that scored three wins in 1996, badged as Petronas in deference to the team's major Malaysian sponsor.
 This agreement to use Ferrari engines lasted until the team's purchase by BMW for .