qa: Create unicode tempdir in test_runner

test/functional/test_runner.py

@@ -229,7 +229,7 @@ def main():
     logging.basicConfig(format='%(message)s', level=logging_level)
 
     # Create base test directory
-    tmpdir = "%s/bitcoin_test_runner_%s" % (args.tmpdirprefix, datetime.datetime.now().strftime("%Y%m%d_%H%M%S"))
+    tmpdir = "%s/test_runner_₿_🏃_%s" % (args.tmpdirprefix, datetime.datetime.now().strftime("%Y%m%d_%H%M%S"))
     os.makedirs(tmpdir)
 
     logging.debug("Temporary test directory at %s" % tmpdir)