log2zulip: Use simpler code for accessing production venv.

The only problem with this resulting code is that setup_path_on_import
only works if the Python versions are the same, so you need to run
this with Python 3 in that case.

We try to resolve that for use on Zulip servers with
zulip/zulip:47c5aae5b242fb6d2f5e860602e0fc0af68419bb; since that's the
main case where the code path runs, that should be good enough.

zulip/integrations/log2zulip/log2zulip

@@ -14,7 +14,7 @@ import traceback
 
 try:
     # Use the Zulip virtualenv if available
-    sys.path.append(os.path.join(os.path.dirname(__file__), "../../.."))
+    sys.path.append("/home/zulip/deployments/current")
     import scripts.lib.setup_path_on_import
 except ImportError:
     pass