Django Evolution 2.1.3 introduced a patch for modern versions of

mysqlclient on Django < 2.0. The patch tried to handle the situation

where mysqlclient wasn't installed, but it didn't catch the right

exception.
This change adds a more broad exception handler, and also exception

handlers in the patch loader, one wrapping needs_patch() and one

wrapping apply_patch(). This will help us avoid other unforeseen

issues in the future.

Ran all unit tests without mysqlclient installed.