Add comment & fix flake8 error

Author: toto6

ot/bregman.py

@@ -344,6 +344,7 @@ def sinkhorn_knopp(a, b, M, reg, numItermax=1000,
 
     # print(reg)
 
+    # Next 3 lines equivalent to K= np.exp(-M/reg), but faster to compute
     K = np.empty(M.shape, dtype=M.dtype)
     np.divide(M, -reg, out=K)
     np.exp(K, out=K)

ot/utils.py

@@ -76,6 +76,7 @@ def clean_zeros(a, b, M):
     b2 = b[b > 0]
     return a2, b2, M2
 
+
 def euclidean_distances(X, Y, squared=False):
     """
     Considering the rows of X (and Y=X) as vectors, compute the