Make base class for data drivers more granular

Some data drivers may not have properties, defined in
the base, also data driver may implement its own
abstract classes.

For example Dynamic Allocator provides a driver
which implements partition_scheme property.

Change-Id: Ifc005db73a7b52c7bf3a5038d28f17e7de05aa98
blueprint: pluggable-do-actions

bareon/drivers/base.py

@@ -29,22 +29,38 @@ class BaseDataDriver(object):
     def __init__(self, data):
         self.data = copy.deepcopy(data)
 
+
+@six.add_metaclass(abc.ABCMeta)
+class PartitioningDataDriverMixin(object):
+
     @abc.abstractproperty
     def partition_scheme(self):
         """Retruns instance of PartionScheme object"""
 
+
+@six.add_metaclass(abc.ABCMeta)
+class ProvisioningDataDriverMixin(object):
+
     @abc.abstractproperty
     def image_scheme(self):
         """Returns instance of ImageScheme object"""
 
-    @abc.abstractproperty
-    def grub(self):
-        """Returns instance of Grub object"""
-
     @abc.abstractproperty
     def operating_system(self):
         """Returns instance of OperatingSystem object"""
 
+
+@six.add_metaclass(abc.ABCMeta)
+class ConfigDriveDataDriverMixin(object):
+
     @abc.abstractproperty
     def configdrive_scheme(self):
         """Returns instance of ConfigDriveScheme object"""
+
+
+@six.add_metaclass(abc.ABCMeta)
+class GrubBootloaderDataDriverMixin(object):
+
+    @abc.abstractproperty
+    def grub(self):
+        """Returns instance of Grub object"""

bareon/drivers/nailgun.py

@@ -24,6 +24,10 @@ from six.moves.urllib.parse import urlsplit
 import yaml
 
 from bareon.drivers.base import BaseDataDriver
+from bareon.drivers.base import ConfigDriveDataDriverMixin
+from bareon.drivers.base import GrubBootloaderDataDriverMixin
+from bareon.drivers.base import PartitioningDataDriverMixin
+from bareon.drivers.base import ProvisioningDataDriverMixin
 from bareon.drivers import ks_spaces_validator
 from bareon import errors
 from bareon import objects
@@ -71,7 +75,11 @@ def match_device(hu_disk, ks_disk):
     return False
 
 
-class Nailgun(BaseDataDriver):
+class Nailgun(BaseDataDriver,
+              PartitioningDataDriverMixin,
+              ProvisioningDataDriverMixin,
+              ConfigDriveDataDriverMixin,
+              GrubBootloaderDataDriverMixin):
     """Driver for parsing regular volumes metadata from Nailgun."""
 
     def __init__(self, data):
@@ -624,7 +632,10 @@ class Ironic(Nailgun):
         return super(Ironic, self).parse_partition_scheme()
 
 
-class NailgunBuildImage(BaseDataDriver):
+class NailgunBuildImage(BaseDataDriver,
+                        ProvisioningDataDriverMixin,
+                        ConfigDriveDataDriverMixin,
+                        GrubBootloaderDataDriverMixin):
 
     # TODO(kozhukalov):
     # This list of packages is used by default only if another