Support coverage 5.0+

[gpotter2]

This is either a bug with coverage.py (nedbat/coveragepy#880) or simply a breaking change.

[codecov]

Codecov Report

Merging #2379 into master will decrease coverage by 0.1%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #2379      +/-   ##
==========================================
- Coverage   87.82%   87.72%   -0.11%     
==========================================
  Files         243      241       -2     
  Lines       50778    50458     -320     
==========================================
- Hits        44598    44264     -334     
- Misses       6180     6194      +14

Impacted Files	Coverage Δ
scapy/compat.py	70.51% <0%> (-7.7%)	⬇️
scapy/autorun.py	78.51% <0%> (-4.14%)	⬇️
scapy/ansmachine.py	84% <0%> (-1%)	⬇️
scapy/layers/inet6.py	81.8% <0%> (-0.22%)	⬇️
scapy/libs/winpcapy.py
scapy/libs/ethertypes.py
scapy/layers/ntp.py	91.77% <0%> (+0.26%)	⬆️

[guedou]

It looks ok. Let's wait for an update from coverage before merging.

[gpotter2]

Fixed in nedbat/coveragepy@842f585
It was a bug, but also our fault for using it wrong: we shouldn't actually use --append (-a) since we have enabled the multiprocessing mode