AppendFileContents will append new `gopkg.FileContents` returned from methods which may return an error It is a convenience function which makes it easier to build up a list of all the required FileContents objects for a package by breaking up their construction into multiple methods, while still allowing proper error handling.

FuncWithContextAndError returns a gopkg.DeclFunc with the given name, args and returnArgs, but with additionally taking a `context.Context` as the first argument and return an `error` as the last return argument.

UnnamedImports returns a `[]gopkg.ImportAndAlias` from a list of import paths.