use f-strings in module utils (#10901)

* use f-strings in module utils

* Apply suggestions from code review

Co-authored-by: Felix Fontein <felix@fontein.de>

* remove unused imports

---------

Co-authored-by: Felix Fontein <felix@fontein.de>

plugins/module_utils/mh/deco.py

@@ -38,7 +38,7 @@ def module_fails_on_exception(func):
     @wraps(func)
     def wrapper(self, *args, **kwargs):
         def fix_key(k):
-            return k if k not in conflict_list else "_" + k
+            return k if k not in conflict_list else f"_{k}"
 
         def fix_var_conflicts(output):
             result = {fix_key(k): v for k, v in output.items()}
@@ -56,7 +56,7 @@ def module_fails_on_exception(func):
         except Exception as e:
             # patchy solution to resolve conflict with output variables
             output = fix_var_conflicts(self.output)
-            msg = "Module failed with exception: {0}".format(str(e).strip())
+            msg = f"Module failed with exception: {str(e).strip()}"
             self.module.fail_json(msg=msg, exception=traceback.format_exc(),
                                   output=self.output, vars=self.vars.output(), **output)
     return wrapper