Transfer gevent errors to log file

Transfer warnings from warnings module to logfile (#2394)

cps/logger.py

@@ -159,6 +159,7 @@ def setup(log_file, log_level=None):
         r.removeHandler(h)
         h.close()
     r.addHandler(file_handler)
+    logging.captureWarnings(True)
     return "" if log_file == DEFAULT_LOG_FILE else log_file
 
 

cps/server.py

@@ -204,6 +204,7 @@ class WebServer(object):
                 output = _readable_listen_address(self.listen_address, self.listen_port)
             log.info('Starting Gevent server on %s', output)
             self.wsgiserver = WSGIServer(sock, self.app, log=self.access_logger, handler_class=MyWSGIHandler,
+                                         error_log=log,
                                          spawn=Pool(), **ssl_args)
             if ssl_args:
                 wrap_socket = self.wsgiserver.wrap_socket