WIP: add az

[raybellwaves]

Closes #78

TODO:

• Wait for next fsspec release
• Run test again
• Add info to README

[raybellwaves]

Currently test is failing at

=============================================== FAILURES ===============================================
__________________________________________ test_dask_parquet ___________________________________________

storage = <azure.storage.blob._blob_service_client.BlobServiceClient object at 0x1170b40d0>

    def test_dask_parquet(storage):
        fs = adlfs.AzureBlobFileSystem(
            account_name=storage.account_name, connection_string=CONN_STR
        )
        fs.mkdir("test")
        STORAGE_OPTIONS = {
            "account_name": "devstoreaccount1",
            "connection_string": CONN_STR,
        }
        df = pd.DataFrame(
            {
                "col1": [1, 2, 3, 4],
                "col2": [2, 4, 6, 8],
                "index_key": [1, 1, 2, 2],
                "partition_key": [1, 1, 2, 2],
            }
        )
    
        dask_dataframe = dd.from_pandas(df, npartitions=1)
        for protocol in ["az", "abfs"]:
>           dask_dataframe.to_parquet(
                "{}://test/test_group.parquet".format(protocol),
                storage_options=STORAGE_OPTIONS,
                engine="pyarrow",
            )

adlfs/tests/test_core.py:488: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
/opt/anaconda3/envs/adlfs-dev/lib/python3.8/site-packages/dask/dataframe/core.py:3947: in to_parquet
    return to_parquet(self, path, *args, **kwargs)
/opt/anaconda3/envs/adlfs-dev/lib/python3.8/site-packages/dask/dataframe/io/parquet/core.py:384: in to_parquet
    fs, _, _ = get_fs_token_paths(path, mode="wb", storage_options=storage_options)
/opt/anaconda3/envs/adlfs-dev/lib/python3.8/site-packages/fsspec/core.py:576: in get_fs_token_paths
    cls = get_filesystem_class(protocol)
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

protocol = 'az'

    def get_filesystem_class(protocol):
        """Fetch named protocol implementation from the registry
    
        The dict ``known_implementations`` maps protocol names to the locations
        of classes implementing the corresponding file-system. When used for the
        first time, appropriate imports will happen and the class will be placed in
        the registry. All subsequent calls will fetch directly from the registry.
    
        Some protocol implementations require additional dependencies, and so the
        import may fail. In this case, the string in the "err" field of the
        ``known_implementations`` will be given as the error message.
        """
        if not protocol:
            protocol = default
    
        if protocol not in registry:
            if protocol not in known_implementations:
>               raise ValueError("Protocol not known: %s" % protocol)
E               ValueError: Protocol not known: az

/opt/anaconda3/envs/adlfs-dev/lib/python3.8/site-packages/fsspec/registry.py:183: ValueError
--------------------------------------- Captured stdout teardown ---------------------------------------
Teardown azurite docker container
======================================= short test summary info ========================================
FAILED adlfs/tests/test_core.py::test_dask_parquet - ValueError: Protocol not known: az

I see the error is coming from az not being known at
https://github.com/intake/filesystem_spec/blob/master/fsspec/registry.py#L88

Do I need to make a PR there as well?

[raybellwaves]

fsspec/filesystem_spec#381

[raybellwaves]

Closing in favor of #111