Fix a Python bytes/int mismatch in CLI tests

Fix a Python bytes/int mismatch in CLI tests

In Python 3.x, a single element of a bytes array is returned as
an integer number. Thus, NEWLINE is an int variable, and attempting
to add it to the line array will fail with a type mismatch error
that may be demonstrated as follows:

    [roam@straylight ~]$ python3 -c 'b"hello" + b"\n"[0]'
    Traceback (most recent call last):
      File "<string>", line 1, in <module>
    TypeError: can't concat int to bytes
    [roam@straylight ~]$