Fix memory leak reading from python ByteBuffer.
Fixes #5913.
`grpc_byte_buffer_reader_next` is documented as 'Caller is responsible
for calling gpr_slice_unref on the result', but that wasn't happening.
This commit adds the missing call to `gpr_slice_unref`.
diff --git a/src/python/grpcio/grpc/_cython/_cygrpc/records.pyx.pxi b/src/python/grpcio/grpc/_cython/_cygrpc/records.pyx.pxi
index c7539f0..e35ecd7 100644
--- a/src/python/grpcio/grpc/_cython/_cygrpc/records.pyx.pxi
+++ b/src/python/grpcio/grpc/_cython/_cygrpc/records.pyx.pxi
@@ -274,6 +274,7 @@
data_slice_length = gpr_slice_length(data_slice)
with gil:
result += (<char *>data_slice_pointer)[:data_slice_length]
+ gpr_slice_unref(data_slice)
with nogil:
grpc_byte_buffer_reader_destroy(&reader)
return bytes(result)