Christian Clauss fdbb3ea4a8
Avoid SyntaxWarning on Python >= 3.8
Avoid [SyntaxWarnings on Python >= 3.8](https://docs.python.org/3/whatsnew/3.8.html#porting-to-python-3-8).

% `python3.8`
```
>>> 0 is 0
<stdin>:1: SyntaxWarning: "is" with a literal. Did you mean "=="?
```
2020-10-13 10:25:14 +02:00
..
2020-02-24 20:41:23 -08:00
2019-03-31 13:39:20 -04:00
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