pytest: test for filtering bug.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

tests/plugins/log.py

@@ -0,0 +1,13 @@
+#!/usr/bin/env python3
+from pyln.client import Plugin
+
+plugin = Plugin()
+
+
+@plugin.init()
+def init(options, configuration, plugin):
+    plugin.log("printing debug log", level='debug')
+    plugin.log("printing info log", level='info')
+
+
+plugin.run()