4.7.8 SQL Incremental Update May Fail for UTF8

The 4.7.8 sql incremental update may fail for anyone running UTF8 for their character set.

Depending on how your database is configured the update will fail when trying to change the image_URL from VARCHAR(256) to VARCHAR(512).

The issue is in this file:
\sites\all\modules\civicrm\CRM\Upgrade\Incremental\sql\4.7.8.mysql.tpl

If your character encoding is latin1, each character is 1 byte - so you can do VARCHAR(767) and not go over InnoDB's "767 characters per column" limit. By comparison, UTF8 has a variable number of bytes per character - up to 3 bytes (or for for UTF8mb4. So you can't go above VARCHAR(255).