tidy-imports is failing when a multiline string is used in a multiline f-string (PyInf#13670)

[saharan-deshaw]

Currently tidy-imports fail when the code contains a multiline string (''' ''') inside a multiline f-string. Reproducer:

$ cat test_tidy.py 
some_fstring = f"""abc
                    {', '.join(['''foo
                                   bar
                                   ''' for a in range(10)])}
"""

$ tidy-imports test_tidy.py
Fails

Opening this issue to fix the above failure.

Thanks.