Oh, this is very bad. Indeed spaces and tabs shouldn't be mixed. It's not fixed, the tabs are still there, although both the forum and GitHub display them as 8 spaces by default
When looking at the code of the PR you can see that the indentation is inconsistent and when selecting the highlighted code you can see that these are tabs.
Anyway, it's good that Py3 raises an error now compared to Py2 where this was allowed. There the behaviour could be quite unexpected when in the editor tab size is set to 4 characters instead of 8.