Improving regexs that scan attributes

[std-max]

Fix #670

[std-max]

Apparently a check failed but @LarsAsplund you have already fixed it in #835

[LarsAsplund]

@std-max Yes, the latest version of Sphinx is a new major version and comes with some backward compatibility breaking changes which I fixed. That is shortly on the master branch and then you can rebase.

[std-max]

CI looks good after rebasing :)

[umarcor]

@std-max do you mind adding some test to make this fix is necessary? I.e., the test should fail without this commit, but pass with it.

[std-max]

Yes, I will add some tests when I have a bit of time 👍