Use raw string literals to prevent syntax warnings when using regular
expressions with backslash-based patterns.
The original code triggered a SyntaxWarning in developer mode (`python3 -Xdev`)
due to unescaped backslash characters in regex patterns like '\s'. While
CPython typically interprets these silently, strict Python parsing modes
raise warnings about potentially unintended escape sequences.
This change adds the `r` prefix to string literals containing regex patterns,
ensuring consistent behavior across different Python runtime configurations
and eliminating unnecessary syntax warning like:
```
/opt/scylladb/scripts/libexec/scylla_io_setup:41: SyntaxWarning: invalid escape sequence '\s'
pattern = re.compile(_nocomment + r"CPUSET=\s*\"" + _reopt(_cpuset) + _reopt(_smp) + "\s*\"")
```
Signed-off-by: Kefu Chai <kefu.chai@scylladb.com>
Closesscylladb/scylladb#21839
a9c244ddf7