To include trailing whitespace on a line in a doctest, _don't_ use raw strings.  Use a regular string, and include add a (one or more) trailing \x20 instead of a space (for example).  For example:

r"""
>>> print("a ")
a 
"""

where there's a space at the end of the output line is no good.  It's visually impossible to tell what's intended, and the commit hook should reject it.  But this works fine (a regular string and an escape code):

"""
>>> print("a ")
a\x20
"""