Declaring the visit of a British warship to Guyana “an intolerable threat,” Venezuelan President Nicolas Maduro on Thursday launched an impromptu military exercise in waters close to its neighbor aiming to show sea and air power amid a border dispute between the two countries. While providing few details about the extent and duration of the exercise, the Venezuelan military said that its initial phase included the participation of about a dozen war vessels, including gunboats and supply ships, and twice as many planes, including fighter jets, in the Gulf of Paria, west of Trinidad, and in fron…