Python code modernization, 1/n (#1141)

* Remove unicode text prefixes.

* Replace str.format() uses with f-strings.

* Replace % with f-strings, and do some cleanup.

* Fix wrong variable.

* Avoid unnecessary string conversion.

plugins/module_utils/_api/credentials/errors.py

@@ -26,12 +26,8 @@ def process_store_error(cpe, program):
     message = cpe.output.decode('utf-8')
     if 'credentials not found in native keychain' in message:
         return CredentialsNotFound(
-            'No matching credentials in {0}'.format(
-                program
-            )
+            f'No matching credentials in {program}'
         )
     return StoreError(
-        'Credentials store {0} exited with "{1}".'.format(
-            program, cpe.output.decode('utf-8').strip()
-        )
+        f'Credentials store {program} exited with "{cpe.output.decode("utf-8").strip()}".'
     )