Error when retrieving UTF-8 strings from database

[JaapJoris]

When submitting a news story that has UTF-8 encoded characters in its title, the submission completes successfully but the resulting redirect produces the following error:

ArgumentError at /
invalid byte sequence in US-ASCII

For some reason, it is falsely assumed that strings returned by Redis are ASCII strings. I have fixed this problem in production by adding the following line to config.ru:

Encoding.default_external = Encoding::UTF_8