Circumvent docutils bug

[flying-sheep]

Fixes #329

[mcmtroffaes]

Oh, swell, glad to have 0.20 out finally! Will merge once tests pass.

[mcmtroffaes]

Some tests need to be fixed for the new docutils; I suspect the format of the generated html has changed slightly.

[codecov]

Codecov Report

Merging #330 (2b73057) into develop (03d924b) will decrease coverage by 0.41%.
The diff coverage is 100.00%.

❗ Current head 2b73057 differs from pull request most recent head 03830da. Consider uploading reports for the commit 03830da to get more accurate results

@@             Coverage Diff             @@
##           develop     #330      +/-   ##
===========================================
- Coverage   100.00%   99.59%   -0.41%     
===========================================
  Files           52       52              
  Lines         2482     2483       +1     
  Branches       435      377      -58     
===========================================
- Hits          2482     2473       -9     
- Misses           0        5       +5     
- Partials         0        5       +5     

Impacted Files	Coverage Δ
test/common.py	78.37% <100.00%> (-21.63%)	⬇️

... and 1 file with indirect coverage changes

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[mcmtroffaes]

Older docutils versions aren't broken, so instead I've gone for excluding 0.18 and 0.19 which are known to be affected by this bug. Thanks again!