Message 367698 - Python tracker
The original issue was about different error messages in REPL and eval(). But it is not related to string prefixes. We have the same difference without involving strings:
>>> a b
File "<stdin>", line 1
a b
^
SyntaxError: invalid syntax
>>> eval("a b")
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "<string>", line 1
a b
^
SyntaxError: unexpected EOF while parsing
I suggest to revert this change and close the issue.