Let's try to sudo nuget restore, then.

Author: asbjornu

.travis.yml

@@ -3,8 +3,7 @@ solution: src/GitVersion.sln
 sudo: true
 install:
   - sudo nuget update -self
-  - sudo -k
-  - nuget restore src/GitVersion.sln
+  - sudo nuget restore src/GitVersion.sln
   - nuget install NUnit.Runners -Version 3.2.1 -OutputDirectory ./src/packages
 script:
   - xbuild "./src/GitVersion.sln" /property:Configuration="Debug" /verbosity:detailed