Fix python config fetch disrupted by stderr output (#13295)

* Fix python config fetch disrupted by stderr output

I have no idea how to make command_runner not include debug output, so just use subprocess.check_output

* restore import

LibreNMS/__init__.py

@@ -9,6 +9,7 @@ from collections import deque
 from logging.handlers import RotatingFileHandler
 from math import ceil
 from queue import Queue
+from subprocess import check_output
 from time import time
 
 from .command_runner import command_runner
@@ -169,10 +170,7 @@ def get_config_data(base_dir):
 
     config_cmd = ["/usr/bin/env", "php", "%s/config_to_json.php" % base_dir]
     try:
-        exit_code, output = command_runner(config_cmd, timeout=300)
-        if exit_code == 0:
-            return json.loads(output)
-        raise EnvironmentError
+        return json.loads(check_output(config_cmd).decode())
     except Exception as exc:
         logger.critical("ERROR: Could not execute command [%s]: %s" % (config_cmd, exc))
         logger.debug("Traceback:", exc_info=True)