nfs: minimal mypy coverage

Add a minimal pass of mypy to nfs.py to
help prevent errors in all of the pending code
changes for this driver.

More complete coverage is in Ide947c8e.

Change-Id: I74bf07f0c5038834c17585245e60000ab6ac8f25

cinder/volume/drivers/nfs.py

@@ -19,6 +19,7 @@ import errno
 import os
 import tempfile
 import time
+import typing
 
 from castellan import key_manager
 from os_brick.remotefs import remotefs as remotefs_brick
@@ -100,9 +101,9 @@ class NfsDriver(remotefs.RemoteFSSnapDriverDistributed):
         self.configuration.append_config_values(nfs_opts)
         root_helper = utils.get_root_helper()
         # base bound to instance is used in RemoteFsConnector.
-        self.base = getattr(self.configuration,
-                            'nfs_mount_point_base')
-        self.base = os.path.realpath(self.base)
+        base = getattr(self.configuration,
+                       'nfs_mount_point_base')
+        self.base = os.path.realpath(base)
         opts = getattr(self.configuration,
                        'nfs_mount_options')
 
@@ -533,7 +534,9 @@ class NfsDriver(remotefs.RemoteFSSnapDriverDistributed):
         data = self._stats
 
         global_capacity = data['total_capacity_gb']
+        global_capacity = typing.cast(float, global_capacity)
         global_free = data['free_capacity_gb']
+        global_free = typing.cast(float, global_free)
 
         thin_enabled = self.configuration.nfs_sparsed_volumes
         if thin_enabled:

mypy-files.txt

@@ -43,6 +43,7 @@ cinder/service.py
 cinder/utils.py
 cinder/volume/__init__.py
 cinder/volume/api.py
+cinder/volume/drivers/nfs.py
 cinder/volume/drivers/rbd.py
 cinder/volume/drivers/remotefs.py
 cinder/volume/flows/api/create_volume.py