TypeError: can not serialize 'Series' object while trying to read remote intake_sql.intake_sql.SQLSource

Using intake-sql.
It seems because msgpack recieve invalid data types in the response.

Traceback (server side) :

```
Traceback (most recent call last):
File "/opt/conda/envs/intake/lib/python3.9/site-packages/tornado/web.py", line 1704, in _execute
result = await result
File "/opt/conda/envs/intake/lib/python3.9/site-packages/tornado/gen.py", line 216, in wrapper
result = ctx_run(func, *args, **kwargs)
File "/opt/conda/envs/intake/lib/python3.9/site-packages/intake/cli/server/server.py", line 329, in post
self.write(msgpack.packb(response, **pack_kwargs))
File "/opt/conda/envs/intake/lib/python3.9/site-packages/msgpack/__init__.py", line 35, in packb
return Packer(**kwargs).pack(o)
File "msgpack/_packer.pyx", line 292, in msgpack._cmsgpack.Packer.pack
File "msgpack/_packer.pyx", line 298, in msgpack._cmsgpack.Packer.pack
File "msgpack/_packer.pyx", line 295, in msgpack._cmsgpack.Packer.pack
File "msgpack/_packer.pyx", line 231, in msgpack._cmsgpack.Packer._pack
File "msgpack/_packer.pyx", line 289, in msgpack._cmsgpack.Packer._pack
TypeError: can not serialize 'Series' object
```