The Python "except Foo as x" syntax was only introduced in
Python 2.6, but we aim to support Python 2.4 and later.
Use the old-style "except Foo, x" syntax instead, thus
fixing configure/compile on systems with older Python.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org> Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>