make bluepyopt tox4 compatible

[codecov-commenter]

Codecov Report

Merging #436 (1ac187f) into master (07c8fbe) will decrease coverage by 0.02%. The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #436      +/-   ##
==========================================
- Coverage   89.77%   89.74%   -0.03%     
==========================================
  Files          46       46              
  Lines        3383     3383              
==========================================
- Hits         3037     3036       -1     
- Misses        346      347       +1     

Impacted Files	Coverage Δ
bluepyopt/deapext/utils.py	95.31% <0.00%> (-1.57%)	:arrow_down:

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