Fix pipetools tests

[gpotter2]

Should fix PyPy freezing on the pipetools tests

[codecov-io]

Codecov Report

Merging #676 into master will decrease coverage by 0.02%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #676      +/-   ##
==========================================
- Coverage   78.89%   78.87%   -0.03%     
==========================================
  Files         128      128              
  Lines       31581    31581              
==========================================
- Hits        24917    24908       -9     
- Misses       6664     6673       +9

Impacted Files	Coverage Δ
scapy/layers/tls/record.py	91.13% <0%> (-1.07%)	⬇️
scapy/layers/tls/cert.py	67.3% <0%> (-0.35%)	⬇️
scapy/layers/tls/handshake.py	80.72% <0%> (-0.32%)	⬇️
scapy/asn1/ber.py	81.23% <0%> (-0.3%)	⬇️
scapy/utils.py	78.59% <0%> (-0.23%)	⬇️
scapy/pipetool.py	92.14% <0%> (+0.21%)	⬆️

[gpotter2]

@guedou Hello, could this be fast-merge ? Should fix the failures of pypy