Printing a formatted float fails when en_US.UTF-8 is not available

```py
print(f"{3.14159265:.2f}")
```

This causes a runtime error when en_US.UTF-8 is not available.

```
ValueError: invalid format specifier: locale::facet::_S_create_c_locale name not valid

Raised from: mstd.internal.format._format_error.0:0
/usr/local/lib/codon/stdlib/internal/format.codon:4:2
```