precertificate failure with findcerts.py

[erbbysam]

findcerts.py does not scan CT precertificates.

This is due to the pyx509 library raising an exception on the critical-marked CT precertificate poison extension - http://www.alvestrand.no/objectid/submissions/1.3.6.1.4.1.11129.2.4.3.html https://github.com/hiviah/pyx509/blob/master/pyx509/pkcs7_models.py#L634