Cert: Tests, Python 3 and Cryptography update

[gpotter2]

For an unknown reason, a few tests are only working locally (not on Appveyor/Travis).
However, they work under Travis Python 3.3

I cannot explain why. They are disabled through the 2nd commit

[codecov-io]

Codecov Report

Merging #1194 into master will increase coverage by 0.21%.
The diff coverage is 56.66%.

@@            Coverage Diff            @@
##           master   #1194      +/-   ##
=========================================
+ Coverage   84.09%   84.3%   +0.21%     
=========================================
  Files         159     159              
  Lines       38211   38228      +17     
=========================================
+ Hits        32133   32230      +97     
+ Misses       6078    5998      -80

Impacted Files	Coverage Δ
scapy/layers/tls/cert.py	82.01% <56.66%> (+12.91%)	⬆️
scapy/__init__.py	83.33% <0%> (-2.39%)	⬇️
scapy/arch/pcapdnet.py	68.77% <0%> (-0.98%)	⬇️
scapy/layers/tls/session.py	74.54% <0%> (-0.41%)	⬇️
scapy/config.py	85.39% <0%> (-0.28%)	⬇️
scapy/fields.py	90.35% <0%> (-0.18%)	⬇️
scapy/layers/inet.py	70.08% <0%> (+0.16%)	⬆️
scapy/sendrecv.py	78.44% <0%> (+0.18%)	⬆️
scapy/asn1/ber.py	82.28% <0%> (+0.28%)	⬆️
scapy/asn1/asn1.py	91.41% <0%> (+1.38%)	⬆️
... and 4 more

[guedou]

@gpotter2 is it related to you cryptography module version ?

[gpotter2]

@guedou You are right, the API has been updated, and our calls have been deprecated. I've updated the ECDSA functions

[gpotter2]

Could you please restart the failing build ? Thanks!

[gpotter2]

Well codecov is broken on OSX Python 3 :/ not related to me though

[guedou]

Awesome PR!