This bug is caused by libhiredis0.14-0.14.0-3 renaming redisReplyReaderGetError to redisReaderGetError.
freeradius-redis may be compiled with another version (<0.14) of libhiredis. libhiredis CHANGELOG: https://github.com/redis/hiredis/blob/3af99d5fd5c2352cd73e851686bb18de122897f1/CHANGELOG.md#0140-2018-09-25 -- If it makes you happy, it can't be that bad.
