diff --git a/tools/run_tests/run_interop_tests.py b/tools/run_tests/run_interop_tests.py
index a3ff453b883..5722a88182b 100755
--- a/tools/run_tests/run_interop_tests.py
+++ b/tools/run_tests/run_interop_tests.py
@@ -689,7 +689,9 @@ def write_cmdlog_maybe(cmdlog, filename):
         with open(filename, 'w') as logfile:
             logfile.write('#!/bin/bash\n')
             logfile.write('# DO NOT MODIFY\n')
-            logfile.write('# This file is generated by run_interop_tests.py/create_testcases.sh\n')
+            logfile.write(
+                '# This file is generated by run_interop_tests.py/create_testcases.sh\n'
+            )
             logfile.writelines("%s\n" % line for line in cmdlog)
         print('Command log written to file %s' % filename)