resolve deprecation warning about serialize_for_cli() (#303)

* resolve deprecation warning about serialize_for_cli()

* linting

* use dask.config.serialize() unconditionally

dask_cloudprovider/generic/vmcluster.py

@@ -11,7 +11,7 @@
 from distributed.scheduler import Scheduler as _Scheduler
 from distributed.security import Security
 from distributed.deploy.spec import SpecCluster, ProcessInterface
-from distributed.utils import warn_on_duration, serialize_for_cli, cli_keywords
+from distributed.utils import warn_on_duration, cli_keywords
 
 from dask_cloudprovider.utils.socket import is_socket_open
 
@@ -31,7 +31,7 @@ def __init__(self, docker_args: str = "", **kwargs):
         self.docker_args = docker_args
         self.auto_shutdown = True
         self.set_env = 'env DASK_INTERNAL_INHERIT_CONFIG="{}"'.format(
-            serialize_for_cli(dask.config.global_config)
+            dask.config.serialize(dask.config.global_config)
         )
         self.kwargs = kwargs