Merge #17488: test: fix "bitcoind already running" warnings on macOS

1c23ea5 test: fix bitcoind already running warnings on macOS (fanquake)

Pull request description:

  On macOS, `pidof` installed via brew returns b'' rather than None.
  Account for this, to remove spurious warnings from the test_runner.

ACKs for top commit:
  laanwj:
    ACK 1c23ea5

Tree-SHA512: 640f4323d4105eac5c7abb52daf80486d5d3b4a074720490ceeb97c3dd8d73a3de9a988d2550f1e2076c620bb10d452b2959d8b723d2ee64f499878909824e31

Author: laanwj

test/functional/test_runner.py

@@ -364,9 +364,10 @@ def main():
 def run_tests(*, test_list, src_dir, build_dir, tmpdir, jobs=1, enable_coverage=False, args=None, combined_logs_len=0, failfast=False, runs_ci, use_term_control):
     args = args or []
 
-    # Warn if bitcoind is already running (unix only)
+    # Warn if bitcoind is already running
+    # pidof might fail or return an empty string if bitcoind is not running
     try:
-        if subprocess.check_output(["pidof", "bitcoind"]) is not None:
+        if subprocess.check_output(["pidof", "bitcoind"]) not in [b'']:
             print("%sWARNING!%s There is already a bitcoind process running on this system. Tests may fail unexpectedly due to resource contention!" % (BOLD[1], BOLD[0]))
     except (OSError, subprocess.SubprocessError):
         pass