Fix python3 only code

[Eagllus]

This should fix: #291 and I think it will fix #286

[codecov-io]

Codecov Report

Merging #292 into master will increase coverage by 0.08%.
The diff coverage is 100%.

@@            Coverage Diff            @@
##           master    #292      +/-   ##
=========================================
+ Coverage   90.12%   90.2%   +0.08%     
=========================================
  Files          44      44              
  Lines        2836    2839       +3     
=========================================
+ Hits         2556    2561       +5     
+ Misses        280     278       -2

Impacted Files	Coverage Δ
django_q/core_signing.py	85% <100%> (ø)	⬆️
django_q/queues.py	100% <100%> (ø)	⬆️
django_q/models.py	98.7% <0%> (+1.29%)	⬆️

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