Bug in multiplication of point by integer #373

from ecdsa.ellipticcurve import INFINITY, CurveFp, Point, PointJacobi

def multiply_naive(point, a):
    ans = point
    for i in range(a-1):
        ans = ans + point
    return ans

curve = CurveFp(p=31, a=2, b=3)
point = Point(curve, 6, 18)
print("point:", point)
print("11*point:", 11*point)
print("11*point (naive):", multiply_naive(point, 11))
print("10*point+point:", 10*point+point)
print("11*point (via Jacobi):", (11*PointJacobi.from_affine(point)).to_affine())

point: (6,18)
11*point: (6,13)
11*point (naive): (8,29)
10*point+point: (8,29)
11*point (via Jacobi): (8,29)