Travis complains about mpl backend
Travis complains about mpl backend

Set to Agg to try to resolve this.
fatiando/fatiando,rafaelmds/fatiando,eusoubrasileiro/fatiando_seismic,cmeessen/fatiando,eusoubrasileiro/fatiando,fatiando/fatiando,mtb-za/fatiando,santis19/fatiando,victortxa/fatiando,drandykass/fatiando,eusoubrasileiro/fatiando,mtb-za/fatiando,drandykass/fatiando,cmeessen/fatiando,victortxa/fatiando,santis19/fatiando,rafaelmds/fatiando,eusoubrasileiro/fatiando,eusoubrasileiro/fatiando_seismic