Hack support for terrible RSA key-lengths in cryptography 43.0

[gpotter2]

• fixes refactor RC2 support to work in an upcoming cryptography release #4285 (comment) and below

[alex]

Thanks!

[codecov]

Codecov Report

Merging #4290 (7bae538) into master (9a91d0e) will increase coverage by 32.31%.
Report is 1 commits behind head on master.
The diff coverage is 58.33%.

Additional details and impacted files

@@             Coverage Diff             @@
##           master    #4290       +/-   ##
===========================================
+ Coverage   49.66%   81.98%   +32.31%     
===========================================
  Files         342      349        +7     
  Lines       76293    81882     +5589     
===========================================
+ Hits        37894    67134    +29240     
+ Misses      38399    14748    -23651     

Files	Coverage Δ
scapy/layers/tls/cert.py	87.15% <58.33%> (+70.31%)	⬆️

... and 264 files with indirect coverage changes