This class represents the exception that is thrown when the user provides
input that uses an instance type, regions or operating system that is not
recognized by our application.
This class represents the specification of a certain EC2 instance, it is
specified by the instance type, the geographical region and the operating
system bneing used.
This class represents the exception that is thrown when the user provides
input that that is not recognized by our application, but it's not caused by
an unknown instance type, region or operating system.