You could pass the errors='ignore', as given below but you need to make sure to check what is a encoding of your files.
open(os.path.join(root, file),'r', encoding='cp932', errors='ignore')
It will not ignore a file completely, but just required characters that cannot be decoded inside your file. Maybe there are only few files or lines incorrectly encoded. You could check that how many of these errors you have by catching your exception and printing a filename.
You can also try using the
io library as given below:
io.open(os.path.join(root, file), mode='r', encoding='cp932')
I am very sure that the above mentioned solutions will be the great help in fixing your error.