test: use f-strings in feature_filelock.py

Author: fanquake

test/functional/feature_filelock.py

@@ -22,11 +22,11 @@ def setup_network(self):
 
     def run_test(self):
         datadir = os.path.join(self.nodes[0].datadir, self.chain)
-        self.log.info("Using datadir {}".format(datadir))
+        self.log.info(f"Using datadir {datadir}")
 
         self.log.info("Check that we can't start a second bitcoind instance using the same datadir")
-        expected_msg = "Error: Cannot obtain a lock on data directory {0}. {1} is probably already running.".format(datadir, self.config['environment']['PACKAGE_NAME'])
-        self.nodes[1].assert_start_raises_init_error(extra_args=['-datadir={}'.format(self.nodes[0].datadir), '-noserver'], expected_msg=expected_msg)
+        expected_msg = f"Error: Cannot obtain a lock on data directory {datadir}. {self.config['environment']['PACKAGE_NAME']} is probably already running."
+        self.nodes[1].assert_start_raises_init_error(extra_args=[f'-datadir={self.nodes[0].datadir}', '-noserver'], expected_msg=expected_msg)
 
         if self.is_wallet_compiled():
             def check_wallet_filelock(descriptors):
@@ -38,7 +38,7 @@ def check_wallet_filelock(descriptors):
                     expected_msg = "Error: SQLiteDatabase: Unable to obtain an exclusive lock on the database, is it being used by another bitcoind?"
                 else:
                     expected_msg = "Error: Error initializing wallet database environment"
-                self.nodes[1].assert_start_raises_init_error(extra_args=['-walletdir={}'.format(wallet_dir), '-wallet=' + wallet_name, '-noserver'], expected_msg=expected_msg, match=ErrorMatch.PARTIAL_REGEX)
+                self.nodes[1].assert_start_raises_init_error(extra_args=[f'-walletdir={wallet_dir}', f'-wallet={wallet_name}', '-noserver'], expected_msg=expected_msg, match=ErrorMatch.PARTIAL_REGEX)
 
             if self.is_bdb_compiled():
                 check_wallet_filelock(False)