#9 a signature which causes loop

[Ray Lance]

Verification goes into an endless loop when I use
sig =
('y+\x00\x006\xdf\xfeKo\xf2\xe31cE\x9a\x06',':\xf3\x00\x00]k\x07\xc3b\x83U\xc2jof\xa7')
with
pubkey =
'KFMnTWdceDAxXHgwMFx4ZTVceGQwXHgxMlx4ZDZceGZiXHgxYjY3XHhlY1x4ODNceDgwXHg4YycKUydVXHg5ZFx4MDFceDAwUlx4YzdceGQ3XHhmNFx4OTVceGZjXHg5OHdceGZhXHhmYmxceDBmJwp0cDEKLg=='
with any text.

How could I protect against this eventuality?