Pip installation issue on MacOS 12.0.2

The error message is quite long, so here's the last bit:


```
SyntaxError: Got error in f-string: Invalid expression: invalid syntax. Got unexpected token ',' at line 408 column 27
        completed_str = f"{completed_ratio:,.{precision}f}"
```

This happens whether I build a version with `ssl` or run `get-pip.py` normally.