Another nice little gotcha for you:
If you get this error after building and installing MySQLdb 1.2.2 on 10.3.9:
have a look in your /usr/local/mysql/lib/ folder. You may discover, as I did, that the library it’s looking for is in that folder, and not in a subfolder called mysql.
I spent ages on this before realising what was wrong.
The solution is simple, just make a mysql subfolder and alias (or copy) the library into it.
Aaaagh!