pytest: fix if no rust installed.

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

tests/test_cln_rs.py

@@ -1,10 +1,8 @@
 from fixtures import *  # noqa: F401,F403
-from node_pb2_grpc import NodeStub
 from pathlib import Path
 from pyln.testing.utils import env, TEST_NETWORK, wait_for
 from ephemeral_port_reserve import reserve
 import grpc
-import node_pb2 as nodepb
 from primitives_pb2 import AmountOrAny
 import pytest
 import subprocess
@@ -74,6 +72,10 @@ def test_plugin_start(node_factory):
 
 def test_grpc_connect(node_factory):
     """Attempts to connect to the grpc interface and call getinfo"""
+    # These only exist if we have rust!
+    from node_pb2_grpc import NodeStub  # noqa: E402
+    import node_pb2 as nodepb  # noqa: E402
+
     grpc_port = reserve()
     bin_path = Path.cwd() / "target" / "debug" / "cln-grpc"
     l1 = node_factory.get_node(options={"plugin": str(bin_path), "grpc-port": str(grpc_port)})
@@ -172,6 +174,10 @@ def test_grpc_wrong_auth(node_factory):
     We create two instances, each generates its own certs and keys,
     and then we try to cross the wires.
     """
+    # These only exist if we have rust!
+    from node_pb2_grpc import NodeStub  # noqa: E402
+    import node_pb2 as nodepb  # noqa: E402
+
     grpc_port = reserve()
     bin_path = Path.cwd() / "target" / "debug" / "cln-grpc"
     l1, l2 = node_factory.get_nodes(2, opts={