asyncio: Make sure BaseException is re-raised in SSLProtocol

Lib/asyncio/sslproto.py

@@ -613,7 +613,8 @@ class SSLProtocol(protocols.Protocol):
                 if data:
                     ssldata, offset = self._sslpipe.feed_appdata(data, offset)
                 elif offset:
-                    ssldata = self._sslpipe.do_handshake(self._on_handshake_complete)
+                    ssldata = self._sslpipe.do_handshake(
+                        self._on_handshake_complete)
                     offset = 1
                 else:
                     ssldata = self._sslpipe.shutdown(self._finalize)
@@ -637,9 +638,13 @@ class SSLProtocol(protocols.Protocol):
                 self._write_buffer_size -= len(data)
         except BaseException as exc:
             if self._in_handshake:
+                # BaseExceptions will be re-raised in _on_handshake_complete.
                 self._on_handshake_complete(exc)
             else:
                 self._fatal_error(exc, 'Fatal error on SSL transport')
+            if not isinstance(exc, Exception):
+                # BaseException
+                raise
 
     def _fatal_error(self, exc, message='Fatal error on transport'):
         # Should be called from exception handler only.