py[BF] fixed another error with old matplotlib versions
py[BF] fixed another error with old matplotlib versions

esc/Psignifit-3.x,esc/Psignifit-3.x,esc/Psignifit-3.x,esc/Psignifit-3.x,esc/Psignifit-3.x,esc/Psignifit-3.x