Experiment: Wrap all capnp code in a context-manager to avoid segfaults (#317)

* Experiment: Wrap all capnp code in a context-manager

* Fix segfault in on_disconnect

test/test_memory_handling.py

@@ -0,0 +1,32 @@
+from types import coroutine
+import pytest
+import socket
+import gc
+
+import capnp
+import test_capability
+import test_capability_capnp as capability
+
+
+@pytest.fixture(autouse=True)
+async def kj_loop():
+    async with capnp.kj_loop():
+        yield
+
+
+@coroutine
+def wrap(p):
+    return (yield from p)
+
+
+async def test_kj_loop_await_attach():
+    read, write = socket.socketpair()
+    read = await capnp.AsyncIoStream.create_connection(sock=read)
+    write = await capnp.AsyncIoStream.create_connection(sock=write)
+    _ = capnp.TwoPartyServer(write, bootstrap=test_capability.Server())
+    client = capnp.TwoPartyClient(read).bootstrap().cast_as(capability.TestInterface)
+    t = wrap(client.foo(5, True).__await__())
+    del client
+    del read
+    gc.collect()
+    await t