travis: run tests with python3
travis: run tests with python3

Signed-off-by: FUJITA Tomonori <93dac1fe9c4b2a3957982200319981492ad4976e@lab.ntt.co.jp>

zyq001/ryu,elahejalalpour/ELRyu,TakeshiTseng/ryu,fujita/ryu,hisaharu/ryu,lagopus/ryu-lagopus-ext,TakeshiTseng/ryu,Zouyiran/ryu,OpenState-SDN/ryu,TakeshiTseng/ryu,pichuang/ryu,sivaramakrishnansr/ryu,diogommartins/ryu,hisaharu/ryu,darjus-amzn/ryu,fujita/ryu,darjus-amzn/ryu,osrg/ryu,lsqtongxin/ryu,iwaseyusuke/ryu,Zouyiran/ryu,OpenState-SDN/ryu,gareging/SDN_Framework,ttsubo/ryu,osrg/ryu,fkakuma/ryu,gareging/SDN_Framework,osrg/ryu,takahashiminoru/ryu,gareging/SDN_Framework,darjus-amzn/ryu,fkakuma/ryu,Tejas-Subramanya/RYU_MEC,sivaramakrishnansr/ryu,diogommartins/ryu,fkakuma/ryu,John-Lin/ryu,darjus-amzn/ryu,zyq001/ryu,ttsubo/ryu,takahashiminoru/ryu,iwaseyusuke/ryu,zangree/ryu,shinpeimuraoka/ryu,StephenKing/ryu,OpenState-SDN/ryu,lsqtongxin/ryu,diogommartins/ryu,zangree/ryu,lagopus/ryu-lagopus-ext,alanquillin/ryu,lsqtongxin/ryu,ttsubo/ryu,takahashiminoru/ryu,alanquillin/ryu,lagopus/ryu-lagopus-ext,zangree/ryu,Tejas-Subramanya/RYU_MEC,hisaharu/ryu,shinpeimuraoka/ryu,iwaseyusuke/ryu,shinpeimuraoka/ryu,iwaseyusuke/ryu,elahejalalpour/ELRyu,habibiefaried/ryu,takahashiminoru/ryu,shinpeimuraoka/ryu,Tejas-Subramanya/RYU_MEC,pichuang/ryu,osrg/ryu,osrg/ryu,gareging/SDN_Framework,fujita/ryu,zyq001/ryu,Zouyiran/ryu,elahejalalpour/ELRyu,StephenKing/ryu,ttsubo/ryu,darjus-amzn/ryu,sivaramakrishnansr/ryu,TakeshiTseng/ryu,lagopus/ryu-lagopus-ext,fkakuma/ryu,OpenState-SDN/ryu,Tejas-Subramanya/RYU_MEC,gareging/SDN_Framework,elahejalalpour/ELRyu,habibiefaried/ryu,John-Lin/ryu,shinpeimuraoka/ryu,ttsubo/ryu,alanquillin/ryu,TakeshiTseng/ryu,John-Lin/ryu,fujita/ryu,zangree/ryu,StephenKing/ryu,Tejas-Subramanya/RYU_MEC,lsqtongxin/ryu,elahejalalpour/ELRyu,diogommartins/ryu,takahashiminoru/ryu,pichuang/ryu,habibiefaried/ryu,lagopus/ryu-lagopus-ext,hisaharu/ryu,zyq001/ryu,zangree/ryu,pichuang/ryu,OpenState-SDN/ryu,fujita/ryu,iwaseyusuke/ryu,habibiefaried/ryu,StephenKing/ryu,alanquillin/ryu,pichuang/ryu,fkakuma/ryu,lsqtongxin/ryu,sivaramakrishnansr/ryu,zyq001/ryu,Zouyiran/ryu,habibiefaried/ryu,Zouyiran/ryu,John-Lin/ryu,sivaramakrishnansr/ryu,alanquillin/ryu,StephenKing/ryu,John-Lin/ryu,diogommartins/ryu,hisaharu/ryu