Try removing Mono apt-get install from Travis.
Try removing Mono apt-get install from Travis.

ddobrev/CppSharp,u255436/CppSharp,Samana/CppSharp,SonyaSa/CppSharp,zillemarco/CppSharp,genuinelucifer/CppSharp,inordertotest/CppSharp,inordertotest/CppSharp,mydogisbox/CppSharp,inordertotest/CppSharp,mono/CppSharp,ktopouzi/CppSharp,ddobrev/CppSharp,mono/CppSharp,SonyaSa/CppSharp,zillemarco/CppSharp,mono/CppSharp,ddobrev/CppSharp,mono/CppSharp,nalkaro/CppSharp,ddobrev/CppSharp,ktopouzi/CppSharp,xistoso/CppSharp,mohtamohit/CppSharp,genuinelucifer/CppSharp,SonyaSa/CppSharp,zillemarco/CppSharp,mydogisbox/CppSharp,xistoso/CppSharp,zillemarco/CppSharp,u255436/CppSharp,zillemarco/CppSharp,nalkaro/CppSharp,xistoso/CppSharp,mydogisbox/CppSharp,u255436/CppSharp,ktopouzi/CppSharp,ktopouzi/CppSharp,mohtamohit/CppSharp,u255436/CppSharp,nalkaro/CppSharp,Samana/CppSharp,Samana/CppSharp,inordertotest/CppSharp,xistoso/CppSharp,xistoso/CppSharp,nalkaro/CppSharp,mydogisbox/CppSharp,mono/CppSharp,ddobrev/CppSharp,mydogisbox/CppSharp,mohtamohit/CppSharp,mohtamohit/CppSharp,mohtamohit/CppSharp,SonyaSa/CppSharp,nalkaro/CppSharp,Samana/CppSharp,SonyaSa/CppSharp,genuinelucifer/CppSharp,genuinelucifer/CppSharp,inordertotest/CppSharp,Samana/CppSharp,genuinelucifer/CppSharp,u255436/CppSharp,ktopouzi/CppSharp,mono/CppSharp