Handle kbi in ctx blocks via `BaseException`

Fixes prior committed tests by more generally handling `BaseExcepion` in
context blocks. Left in the commented concrete list for reference.

tractor/_portal.py

@@ -177,7 +177,6 @@ class Portal:
                 f"Cancelling all streams with {self.channel.uid}")
             for stream in self._streams.copy():
                 try:
-                    # with trio.CancelScope(shield=True):
                     await stream.aclose()
                 except trio.ClosedResourceError:
                     # don't error the stream having already been closed
@@ -294,7 +293,6 @@ class Portal:
     async def open_stream_from(
         self,
         async_gen_func: Callable,  # typing: ignore
-        shield: bool = False,
         **kwargs,
 
     ) -> AsyncGenerator[ReceiveMsgStream, None]:
@@ -318,11 +316,17 @@ class Portal:
         # receive only stream
         assert functype == 'asyncgen'
 
-        ctx = Context(self.channel, cid, _portal=self)
+        ctx = Context(
+            self.channel,
+            cid,
+            # do we need this to be closed implicitly?
+            # _recv_chan=recv_chan,
+            _portal=self
+        )
         try:
             # deliver receive only stream
             async with ReceiveMsgStream(
-                ctx, recv_chan, shield=shield
+                ctx, recv_chan,
             ) as rchan:
                 self._streams.add(rchan)
                 yield rchan
@@ -337,13 +341,16 @@ class Portal:
             # message right now since there shouldn't be a reason to
             # stop and restart the stream, right?
             try:
-                await ctx.cancel()
+                with trio.CancelScope(shield=True):
+                    await ctx.cancel()
 
             except trio.ClosedResourceError:
                 # if the far end terminates before we send a cancel the
                 # underlying transport-channel may already be closed.
-                log.debug(f'Context {ctx} was already closed?')
+                log.warning(f'Context {ctx} was already closed?')
 
+            # XXX: should this always be done?
+            # await recv_chan.aclose()
             self._streams.remove(rchan)
 
     @asynccontextmanager
@@ -408,8 +415,8 @@ class Portal:
 
                 # pairs with handling in ``Actor._push_result()``
                 # recv_chan._ctx = ctx
-
                 # await trio.lowlevel.checkpoint()
+
                 yield ctx, first
 
         except ContextCancelled as err:
@@ -427,9 +434,14 @@ class Portal:
                 log.debug(f'Context {ctx} cancelled gracefully')
 
         except (
-            trio.Cancelled,
-            trio.MultiError,
-            Exception,
+            BaseException,
+
+            # more specifically, we need to handle:
+            # Exception,
+            # trio.Cancelled,
+            # trio.MultiError,
+            # KeyboardInterrupt,
+
         ) as err:
             _err = err
             # the context cancels itself on any cancel
@@ -440,6 +452,11 @@ class Portal:
             raise
 
         finally:
+            # in the case where a runtime nursery (due to internal bug)
+            # or a remote actor transmits an error we want to be
+            # sure we get the error the underlying feeder mem chan.
+            # if it's not raised here it *should* be raised from the
+            # msg loop nursery right?
             result = await ctx.result()
 
             # though it should be impossible for any tasks