handle not having aiohttp_socks

Index: hass_pyscript_kernel/shim.py
--- hass_pyscript_kernel/shim.py.orig
+++ hass_pyscript_kernel/shim.py
@@ -23,7 +23,10 @@ from typing import Any
 import aiohttp
 from aiohttp import ClientResponse
 from aiohttp.typedefs import StrOrURL
-import aiohttp_socks as proxy
+try:
+    import aiohttp_socks as proxy
+except ImportError:
+    proxy = None
 from jupyter_client.kernelspec import KernelSpecManager
 
 #
@@ -106,6 +109,9 @@ class RelayPort:
                 await status_q.put(["task_start", asyncio.current_task()])
 
                 if CONFIG_SETTINGS["hass_proxy"] is not None:
+                    if proxy is None:
+                        print(f"{PKG_NAME}: configured to use proxy, but aiohttp_socks unavailable")
+                        sys.exit(1)
                     if self.verbose >= 3:
                         print(
                             f"{PKG_NAME}: {self.name} connected to jupyter client; now trying pyscript kernel"
