f-strings: fix nested string literals
f-strings: fix nested string literals

ChristopherHogan/cython,da-woods/cython,ChristopherHogan/cython,c-blake/cython,scoder/cython,fabianrost84/cython,scoder/cython,cython/cython,da-woods/cython,scoder/cython,da-woods/cython,cython/cython,fabianrost84/cython,c-blake/cython,cython/cython,da-woods/cython,fabianrost84/cython,ChristopherHogan/cython,c-blake/cython,fabianrost84/cython,c-blake/cython,c-blake/cython,cython/cython,scoder/cython,fabianrost84/cython