comment to explain sleep

lib/extensions/print_pdf.py

@@ -294,7 +294,12 @@ class Print(InkstitchExtension):
             realistic_color_block_svgs=realistic_color_block_svgs
         )
         print_server.start()
+
+        # Wait for print_server.host and print_server.port to be populated.
+        # Hacky, but Flask doesn't have an option for a callback to be run
+        # after startup.
         time.sleep(0.5)
+
         browser_window = open_url("http://%s:%s/" % (print_server.host, print_server.port))
         browser_window.wait()
         print_server.stop()