pyln: Add unit tests from pyln-* to `make check-python`

Makefile

@@ -314,9 +314,10 @@ check-python:
 	@# E501 line too long (N > 79 characters)
 	@# E731 do not assign a lambda expression, use a def
 	@# W503: line break before binary operator
-	@flake8 --ignore=E501,E731,W503 --exclude=contrib/pylightning/lightning/__init__.py ${PYSRC}
+	@flake8 --ignore=E501,E731,W503 ${PYSRC}
 
 	PYTHONPATH=contrib/pyln-client:$$PYTHONPATH $(PYTEST) contrib/pyln-client/
+	PYTHONPATH=contrib/pyln-proto:$$PYTHONPATH $(PYTEST) contrib/pyln-proto/
 
 check-includes:
 	@tools/check-includes.sh

contrib/pylightning/lightning/__init__.py

@@ -1 +1,10 @@
 from pyln.client import LightningRpc, RpcError, Millisatoshi, __version__, Plugin, monkey_patch
+
+__all__ = [
+    "__version__",
+    "LightningRpc",
+    "RpcError",
+    "Millisatoshi",
+    "Plugin",
+    "monkey_patch",
+]