http: Use print for stderr too.

Avoids hardcoding newline char.

caucase/http.py

@@ -181,13 +181,14 @@ class CaucaseSSLWSGIRequestHandler(CaucaseWSGIRequestHandler):
   def log_message(self, format, *args):
     # Note: compared to BaseHTTPHandler, logs the client certificate serial as
     # user name.
-    sys.stderr.write(
-      "%s - %s [%s] %s\n" % (
+    print(
+      "%s - %s [%s] %s" % (
         self.client_address[0],
         self.ssl_client_cert_serial,
         self.log_date_time_string(),
         format % args,
-      )
+      ),
+      file=sys.stderr,
     )
   # pylint: enable=redefined-builtin
 
@@ -662,12 +663,13 @@ def main(argv=None, until=utils.until):
       if host in known_host_set:
         continue
       known_host_set.add(host)
-      sys.stderr.write(
-        'Listening on [%s]:%i-%i\n' % (
+      print(
+        'Listening on [%s]:%i-%i' % (
           host,
           http_port,
           https_port,
         ),
+        file=sys.stderr,
       )
       http_list.append(
         make_server(
@@ -780,7 +782,7 @@ def main(argv=None, until=utils.until):
   except utils.SleepInterrupt:
     pass
   finally:
-    sys.stderr.write('Exiting\n')
+    print('Exiting', file=sys.stderr)
     for server in itertools.chain(http_list, https_list):
       server.server_close()
       server.shutdown()