test: use pgrep for better compatibility

pidof is not available on BSD system, while pgrep is present on BSD, Linux and macOS

Author: S3RK

test/functional/test_runner.py

@@ -396,11 +396,12 @@ def run_tests(*, test_list, src_dir, build_dir, tmpdir, jobs=1, enable_coverage=
     args = args or []
 
     # 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"]) not in [b'']:
+        # pgrep exits with code zero when one or more matching processes found
+        if subprocess.run(["pgrep", "-x", "bitcoind"], stdout=subprocess.DEVNULL).returncode == 0:
             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):
+    except OSError:
+        # pgrep not supported
         pass
 
     # Warn if there is a cache directory