fix syntaxwarning in disk encryption suite

Author: strtgbb

disk_level_encryption/tests/steps.py

@@ -448,7 +448,7 @@ def get_random_string(self, length, cluster=None, steps=True, *args, **kwargs):
     with tempfile.NamedTemporaryFile("w+", encoding="utf-8") as fd:
         cluster.command(
             None,
-            f"cat /dev/urandom | tr -dc 'A-Za-z0-9#$&()*+,-./:;<=>?@[\]^_~' | head -c {length} > {fd.name}",
+            rf"cat /dev/urandom | tr -dc 'A-Za-z0-9#$&()*+,-./:;<=>?@[\]^_~' | head -c {length} > {fd.name}",
             steps=steps,
             *args,
             **kwargs,