The error says that the CourseRepository can not be initialized because it does not have parameter less constructor. Mocking framework looks for parameter less constructor first to create mock object.
If your class does not have parameterless constructor then you need to pass those parameters when you create Mock. In your case mock of CourseRepository would be created as following.
var repositoryMock = new Mock<CourseRepository>(null);
Instead of null, you can pass mock objects of the constructor parameters also.