to the north , the external threat that might have been posed by france was in abeyance , since king louis was busy getting rid of the last of the english invaders , and facing up to the problems the duke of burgundy was causing him ; while to the south , pope sixtus iv , a potential ally of the pazzi , was too busy promoting his relatives and supervising the construction of a magnificent new chapel in the vatican to give much thought to interference in tuscany .