test, contrib, refactor: use with when opening a file

test/functional/feature_config_args.py

@@ -247,7 +247,8 @@ class ConfArgsTest(BitcoinTestFramework):
         conf_file = os.path.join(default_data_dir, "bitcoin.conf")
 
         # datadir needs to be set before [chain] section
-        conf_file_contents = open(conf_file, encoding='utf8').read()
+        with open(conf_file, encoding='utf8') as f:
+            conf_file_contents = f.read()
         with open(conf_file, 'w', encoding='utf8') as f:
             f.write(f"datadir={new_data_dir}\n")
             f.write(conf_file_contents)

test/functional/feature_versionbits_warning.py

@@ -58,7 +58,8 @@ class VersionBitsWarningTest(BitcoinTestFramework):
 
     def versionbits_in_alert_file(self):
         """Test that the versionbits warning has been written to the alert file."""
-        alert_text = open(self.alert_filename, 'r', encoding='utf8').read()
+        with open(self.alert_filename, 'r', encoding='utf8') as f:
+            alert_text = f.read()
         return VB_PATTERN.search(alert_text) is not None
 
     def run_test(self):

test/util/test_runner.py

@@ -22,7 +22,8 @@ import sys
 def main():
     config = configparser.ConfigParser()
     config.optionxform = str
-    config.read_file(open(os.path.join(os.path.dirname(__file__), "../config.ini"), encoding="utf8"))
+    with open(os.path.join(os.path.dirname(__file__), "../config.ini"), encoding="utf8") as f:
+        config.read_file(f)
     env_conf = dict(config.items('environment'))
 
     parser = argparse.ArgumentParser(description=__doc__)
@@ -43,7 +44,8 @@ def main():
 def bctester(testDir, input_basename, buildenv):
     """ Loads and parses the input file, runs all tests and reports results"""
     input_filename = os.path.join(testDir, input_basename)
-    raw_data = open(input_filename, encoding="utf8").read()
+    with open(input_filename, encoding="utf8") as f:
+        raw_data = f.read()
     input_data = json.loads(raw_data)
 
     failed_testcases = []
@@ -80,7 +82,8 @@ def bctest(testDir, testObj, buildenv):
     inputData = None
     if "input" in testObj:
         filename = os.path.join(testDir, testObj["input"])
-        inputData = open(filename, encoding="utf8").read()
+        with open(filename, encoding="utf8") as f:
+            inputData = f.read()
         stdinCfg = subprocess.PIPE
 
     # Read the expected output data (if there is any)
@@ -91,7 +94,8 @@ def bctest(testDir, testObj, buildenv):
         outputFn = testObj['output_cmp']
         outputType = os.path.splitext(outputFn)[1][1:]  # output type from file extension (determines how to compare)
         try:
-            outputData = open(os.path.join(testDir, outputFn), encoding="utf8").read()
+            with open(os.path.join(testDir, outputFn), encoding="utf8") as f:
+                outputData = f.read()
         except:
             logging.error("Output file " + outputFn + " cannot be opened")
             raise