playwright: Improve error message (and make it trigger always) for wh…

…en LOCUST_PLAYWRIGHT is unset.

locust_plugins/users/playwright.py

@@ -1,17 +1,19 @@
+import logging
+import os
+import sys
 try:
     from playwright.async_api import async_playwright, Playwright, Browser, Page, BrowserContext
-except NotImplementedError as e:
-    raise Exception(
-        "Could not import playwright, probably because gevent monkey patching was done before trio init. Set env var LOCUST_PLAYWRIGHT=1"
-    ) from e
+except (NotImplementedError, AttributeError) as e:
+    if os.getenv("LOCUST_PLAYWRIGHT", False):
+        raise Exception("Could not import playwright, even though LOCUST_PLAYWRIGHT was set :(") from e
+    else:
+        logging.error("Set env var LOCUST_PLAYWRIGHT=1 to make locust load trio before gevent monkey patching")
+        sys.exit(1)
 from contextlib import asynccontextmanager, contextmanager
-import logging
-import os
 import asyncio
 from locust import User, events, task
 from locust.runners import WorkerRunner
 import gevent
-import sys
 import ast
 import types
 import time