Merge pull request #2657 from cyclaero/conditional-sigusr1

Windows does not support SIGUSR1, so don't use it unconditionally.

searx/search/checker/background.py

@@ -94,6 +94,8 @@ def _signal_handler(signum, frame):
 
 
 def initialize():
+    if hasattr(signal, 'SIGUSR1'):
+        # Windows doesn't support SIGUSR1
         logger.info('Send SIGUSR1 signal to pid %i to start the checker', os.getpid())
         signal.signal(signal.SIGUSR1, _signal_handler)