don't build readthedocs epub

[graingert]

Change suggested by @adiroiban, I'm -0 on this as it's not doing too much harm

Contributor Checklist:

• I have updated the release notes at docs/source/NEWS.rst
• I have updated the automated tests.
• All tests pass on your local dev environment. See CONTRIBUTING.rst.

[codecov]

Codecov Report

Merging #190 (641e843) into master (df81510) will increase coverage by 10.34%.
The diff coverage is n/a.

❗ Current head 641e843 differs from pull request most recent head 84ece14. Consider uploading reports for the commit 84ece14 to get more accurate results

@@             Coverage Diff             @@
##           master     #190       +/-   ##
===========================================
+ Coverage   83.28%   93.63%   +10.34%     
===========================================
  Files          87       74       -13     
  Lines       11567    10420     -1147     
  Branches     1184     1071      -113     
===========================================
+ Hits         9634     9757      +123     
+ Misses       1815      544     -1271     
- Partials      118      119        +1     

Impacted Files	Coverage Δ
ldaptor/usage.py	69.35% <0.00%> (-11.30%)	⬇️
ldaptor/protocols/pureber.py	89.03% <0.00%> (-1.72%)	⬇️
ldaptor/protocols/ldap/ldapsyntax.py	93.05% <0.00%> (-1.20%)	⬇️
ldaptor/protocols/ldap/ldapserver.py	80.98% <0.00%> (-0.87%)	⬇️
ldaptor/protocols/ldap/ldifdelta.py	89.90% <0.00%> (-0.84%)	⬇️
ldaptor/ldiftree.py	88.92% <0.00%> (-0.64%)	⬇️
ldaptor/entry.py	94.66% <0.00%> (-0.37%)	⬇️
ldaptor/dns.py	93.47% <0.00%> (ø)
ldaptor/config.py	74.28% <0.00%> (ø)
ldaptor/checkers.py	0.00% <0.00%> (ø)
... and 76 more

---

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[adiroiban]

I am +1 since I hope that with this we get a green Read the docs badge.

I like to check the readme or github repo start page and see the status of all the tests.

I now see that we don't run the read the docs tests on a merge in master.
Not sure if that is on purpose... or this is how read that docs works

Does read the docs run the commit tests only for a PR, or it can also run the tests and send a commit status for a push/merge?

[graingert]

I am +1 since I hope that with this we get a green Read the docs badge.

The readthedocs badge is already green

[adiroiban]

If Read the docs is not creating the EPUB during a PR tests, I think is best have this merged. Thanks!

[glyph]

I'm 👍 on green checkmarks

[glyph]

I would have merged this but python3.6 has been removed from github actions so the build config needs to be updated first :(

[psi29a]

Going to push this through, it removal of epub creation which has no effect on code itself.