Returns the response file path for a Github path

Property definitions

github $ MockGithubAPI :: response_file
	# Returns the response file path for a Github `path`
	fun response_file(path: String): String do
		assert has_response(path)
		return "{responses_dir / test_responses[path]}.res"
	end
lib/github/tests/test_api.nit:98,2--102,4