Allow collection to be on file system while catalog is in the cloud

[wachsylon]

When using an esm_collection from file system:

intake.open_esm_datastore('/home/dkrz/k204210/intake-esm/esm-collections/dkrz_era5_disk_grb_fromcloud.json')

with url as catalog_file entry value:

cat /home/dkrz/k204210/intake-esm/esm-collections/dkrz_era5_disk_grb_fromcloud.json
...
  "catalog_file": "https://swift.dkrz.de/v1/dkrz_a44962e3ba914c309a7421573a6949a6/intake-esm/dkrz_era5_disk_grb.csv.gz",

results in

Unable to find: /home/dkrz/k204210/intake-esm/esm-collections/https:/swift.dkrz.de/v1/dkrz_a44962e3ba914c309a7421573a6949a6/intake-esm/dkrz_era5_disk_grb.csv.gz

I think there is no reason why this should not work.

[andersy005]

@wachsylon, I concur with you. This is a bug in _fetch_catalog function, and we should relax some of the assumptions made in this function

intake-esm/intake_esm/utils.py

Line 64 in 3092400

def _fetch_catalog(collection_data, esmcol_path, csv_kwargs=None):

I am happy to look into it, but if you have time and are interested in working on it, please feel free to submit a PR :)