Backwards compatibility for python 2.4
Backwards compatibility for python 2.4

Python 2.4 doesn't allow try...except...finally clauses, see PEP
341. Also, yield statements inside try...finally is not allowed. The
commit changes the logic to no longer use those syntactical features.

Signed-off-by: Nicolas Sebrecht <bfde528c540959b0444735ff13b324b56e999b57@laposte.net>

frioux/offlineimap,frioux/offlineimap