Python 3.10 support

[elacuesta]

Closes #412

[codecov]

Codecov Report

Merging #415 (c7375ed) into master (1c661ba) will increase coverage by 0.04%.
The diff coverage is n/a.

❗ Current head c7375ed differs from pull request most recent head 2d38b47. Consider uploading reports for the commit 2d38b47 to get more accurate results

@@            Coverage Diff             @@
##           master     #415      +/-   ##
==========================================
+ Coverage   89.48%   89.52%   +0.04%     
==========================================
  Files          34       34              
  Lines        2415     2415              
==========================================
+ Hits         2161     2162       +1     
+ Misses        254      253       -1     

Impacted Files	Coverage Δ
shub/image/deploy.py	95.10% <0.00%> (+0.69%)	⬆️

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[Gallaecio]

Upstream seems to be looking for a reproducible example for this bug. Any chance you can work one out? I fear they may close the issue without addressing it otherwise.