intake server leads to ERROR: KeyError('xarray')

### Description

I tried out the intake-server. In the end, I would like to have a server for some or all cats of:
https://swiftbrowser.dkrz.de/public/dkrz_a44962e3ba914c309a7421573a6949a6/intake-esm/
The entry catalog is
`dkrz_data-pool_cloudcatalog.yaml`

I started the server from the same environment as from where I did client commands. I installed intake_xarray as well.

Do you have an idea what the problem is? I saw that the remote catalog wants to use sth like `container: xarray` what I do not really understand. What is a container? Why xarray?

### What I Did

```
cat > temp.yaml <EOF
intake-server temp.yaml 1>log 2>&1 &
intake list --full intake://localhost:8898
ERROR: KeyError('xarray')

cat log
2022-02-10 17:33:05,850 - intake - INFO - __main__.py:main:L53 - Creating catalog from:
2022-02-10 17:33:05,850 - intake - INFO - __main__.py:main:L55 - - temp.yaml
2022-02-10 17:33:06,509 - intake - INFO - __main__.py:main:L62 - catalog_args: temp.yaml
2022-02-10 17:33:06,509 - intake - INFO - __main__.py:main:L70 - Listening on localhost:8898
2022-02-10 17:33:06,509 - intake - DEBUG - server.py:__init__:L32 - auth: {'cls': 'intake.auth.base.BaseAuth'}
2022-02-10 17:33:38,289 - intake - DEBUG - server.py:post:L241 - Source POST: {'action': 'open', 'name': 'dkrz_cmip6_cloud_zarr', 'parameters': {}, 'available_plugins': ['yaml_file_cat', 'yaml_files_cat', 'netcdf', 'opendap', 'rasterio', 'remote-xarray', 'xarray_image', 'zarr', 'alias', 'catalog', 'csv', 'intake_remote', 'json', 'jsonl', 'ndzarr', 'numpy', 'textfiles', 'tiled', 'tiled_cat', 'zarr_cat', 'esm_datastore', 'esm_group', 'esm_single_source']}
2022-02-10 17:33:38,289 - intake - DEBUG - server.py:post:L302 - Opening entry
2022-02-10 17:33:38,289 - intake - DEBUG - server.py:add:L146 - Adding to cache, uuid 329a34f5-4eb0-40de-a4e0-089b3a43e7e2
2022-02-10 17:33:38,289 - intake - DEBUG - server.py:post:L314 - Container: xarray, ID: 329a34f5-4eb0-40de-a4e0-089b3a43e7e2

ipython
import intake
import intake_esm
import intake_xarray
test=intake.open_catalog("intake://localhost:8898")
list(test)
Out[22]: ['dkrz_cmip6_cloud_zarr']

In [24]: test["dkrz_cmip6_cloud_zarr"]
---------------------------------------------------------------------------
KeyError Traceback (most recent call last)
Input In [24], in
----> 1 test["dkrz_cmip6_cloud_zarr"]

File ~/.conda/envs/appmode/lib/python3.10/site-packages/intake/catalog/base.py:436, in Catalog.__getitem__(self, key)
427 """Return a catalog entry by name.
428
429 Can also use attribute syntax, like ``cat.entry_name``, or
(...)
432 cat['name1', 'name2']
433 """
434 if not isinstance(key, list) and key in self:
435 # triggers reload_on_change
--> 436 s = self._get_entry(key)
437 if s.container == 'catalog':
438 s.name = key

File ~/.conda/envs/appmode/lib/python3.10/site-packages/intake/catalog/utils.py:45, in reload_on_change..wrapper(self, *args, **kwargs)
42 @functools.wraps(f)
43 def wrapper(self, *args, **kwargs):
44 self.reload()
---> 45 return f(self, *args, **kwargs)

File ~/.conda/envs/appmode/lib/python3.10/site-packages/intake/catalog/base.py:323, in Catalog._get_entry(self, name)
321 ups = [up for name, up in self.user_parameters.items() if name not in up_names]
322 entry._user_parameters = ups + (entry._user_parameters or [])
--> 323 return entry()

File ~/.conda/envs/appmode/lib/python3.10/site-packages/intake/catalog/entry.py:77, in CatalogEntry.__call__(self, persist, **kwargs)
75 raise ValueError('Persist value (%s) not understood' % persist)
76 persist = persist or self._pmode
---> 77 s = self.get(**kwargs)
78 if persist != 'never' and isinstance(s, PersistMixin) and s.has_been_persisted:
79 from ..container.persist import store

File ~/.conda/envs/appmode/lib/python3.10/site-packages/intake/catalog/remote.py:459, in RemoteCatalogEntry.get(self, **user_parameters)
457 http_args['headers'] = self.http_args['headers'].copy()
458 http_args['headers'].update(self.auth.get_headers())
--> 459 return open_remote(
460 self.url, self.name, container=self.container,
461 user_parameters=user_parameters, description=self.description,
462 http_args=http_args,
463 page_size=self._page_size,
464 auth=self.auth,
465 getenv=self.getenv,
466 persist_mode=self.catalog_pmode,
467 getshell=self.getshell)

File ~/.conda/envs/appmode/lib/python3.10/site-packages/intake/catalog/remote.py:515, in open_remote(url, entry, container, user_parameters, description, http_args, page_size, persist_mode, auth, getenv, getshell)
506 if container == 'catalog':
507 response.update({'auth': auth,
508 'getenv': getenv,
509 'getshell': getshell,
(...)
513 # TODO storage_options?
514 })
--> 515 source = container_map[container](url, http_args, **response)
516 source.description = description
517 return source

File ~/.conda/envs/appmode/lib/python3.10/site-packages/intake_xarray/xarray_container.py:91, in RemoteXarray.__init__(self, url, headers, **kwargs)
78 """
79 Initialise local xarray, whose dask arrays contain tasks that pull data
80
(...)
88 server.
89 """
90 import xarray as xr
---> 91 super(RemoteXarray, self).__init__(url, headers, **kwargs)
92 self._schema = None
93 self._ds = xr.open_zarr(self.metadata['internal'])

File ~/.conda/envs/appmode/lib/python3.10/site-packages/intake/container/base.py:44, in RemoteSource.__init__(self, url, headers, name, parameters, metadata, **kwargs)
42 self._source_id = None
43 self.metadata = metadata or {}
---> 44 self._get_source_id()

File ~/.conda/envs/appmode/lib/python3.10/site-packages/intake/container/base.py:55, in RemoteSource._get_source_id(self)
53 req.raise_for_status()
54 response = msgpack.unpackb(req.content, **unpack_kwargs)
---> 55 self._parse_open_response(response)

File ~/.conda/envs/appmode/lib/python3.10/site-packages/intake/container/base.py:58, in RemoteSource._parse_open_response(self, response)
57 def _parse_open_response(self, response):
---> 58 dtype_descr = response['dtype']
59 if isinstance(dtype_descr, list):
60 # Reformat because NumPy needs list of tuples
61 dtype_descr = [tuple(x) for x in response['dtype']]

KeyError: 'dtype'

```

### Version information: output of `intake_esm.show_versions()`

Paste the output of `intake_esm.show_versions()` here:

```python
import intake_esm

intake_esm.show_versions()

INSTALLED VERSIONS
------------------

cftime: 1.5.2
dask: 2022.01.1
fastprogress: 0.2.7
fsspec: 2022.01.0
gcsfs: None
intake: 0.6.5
intake_esm: 2021.8.17
netCDF4: 1.5.8
pandas: 1.3.5
requests: 2.27.1
s3fs: None
xarray: 0.21.1
zarr: 2.11.0

```

Reproduce the failure with the shown temp.yaml and intake-server command, then trace the remote entry through intake/catalog/remote.py, intake_xarray/xarray_container.py, and intake/container/base.py as shown in the traceback. Check the server response for the missing dtype field and compare it with the available intake plugins and installed versions. Done means the remote catalog entry opens without the reported KeyError.

Written by the indexing model from the issue text.