Fix "No documentation found in" errors in docs

This commit removes errors like:

 Warning: No documentation found in
          sqlalchemy = oslo_db.sqlalchemy.migration

It's done either by removing pages referring to oslo's completely or
adding proper documentation to classes.

Change-Id: I145464d0d63cb5a00e0e905083c260fb6621dd89
Closes-Bug: 1663527

cinder/scheduler/weights/capacity.py

@@ -15,30 +15,6 @@
 #    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 #    License for the specific language governing permissions and limitations
 #    under the License.
-"""
-Weighers that weigh hosts by their capacity, including following two
-weighers:
-
-1. Capacity Weigher.  Weigh hosts by their virtual or actual free capacity.
-
-For thin provisioning, weigh hosts by their virtual free capacity calculated
-by the total capacity multiplied by the max over subscription ratio and
-subtracting the provisioned capacity; Otherwise, weigh hosts by their actual
-free capacity, taking into account the reserved space.
-
-The default is to spread volumes across all hosts evenly.  If you prefer
-stacking, you can set the 'capacity_weight_multiplier' option to a negative
-number and the weighing has the opposite effect of the default.
-
-2. Allocated Capacity Weigher.  Weigh hosts by their allocated capacity.
-
-The default behavior is to place new volume to the host allocated the least
-space.  This weigher is intended to simulate the behavior of SimpleScheduler.
-If you prefer to place volumes to host allocated the most space, you can
-set the 'allocated_capacity_weight_multiplier' option to a positive number
-and the weighing has the opposite effect of the default.
-"""
-
 
 import math
 
@@ -67,6 +43,18 @@ OFFSET_MULT = 100
 
 
 class CapacityWeigher(weights.BaseHostWeigher):
+    """Capacity Weigher weighs hosts by their virtual or actual free capacity.
+
+    For thin provisioning, weigh hosts by their virtual free capacity
+    calculated by the total capacity multiplied by the max over subscription
+    ratio and subtracting the provisioned capacity; Otherwise, weigh hosts by
+    their actual free capacity, taking into account the reserved space.
+
+    The default is to spread volumes across all hosts evenly. If you prefer
+    stacking, you can set the ``capacity_weight_multiplier`` option to a
+    negative number and the weighing has the opposite effect of the default.
+
+    """
     def weight_multiplier(self):
         """Override the weight multiplier."""
         return CONF.capacity_weight_multiplier
@@ -138,6 +126,15 @@ class CapacityWeigher(weights.BaseHostWeigher):
 
 
 class AllocatedCapacityWeigher(weights.BaseHostWeigher):
+    """Allocated Capacity Weigher weighs hosts by their allocated capacity.
+
+    The default behavior is to place new volume to the host allocated the least
+    space. This weigher is intended to simulate the behavior of
+    SimpleScheduler. If you prefer to place volumes to host allocated the most
+    space, you can set the ``allocated_capacity_weight_multiplier`` option to a
+    positive number and the weighing has the opposite effect of the default.
+    """
+
     def weight_multiplier(self):
         """Override the weight multiplier."""
         return CONF.allocated_capacity_weight_multiplier

cinder/scheduler/weights/chance.py

@@ -11,12 +11,6 @@
 # WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 # License for the specific language governing permissions and limitations
 # under the License.
-"""
-Chance Weigher.  Assign random weights to hosts.
-
-Used to spread volumes randomly across a list of equally suitable hosts.
-"""
-
 
 import random
 
@@ -24,5 +18,9 @@ from cinder.scheduler import weights
 
 
 class ChanceWeigher(weights.BaseHostWeigher):
+    """Chance Weigher assigns random weights to hosts.
+
+    Used to spread volumes randomly across a list of equally suitable hosts.
+    """
     def _weigh_object(self, host_state, weight_properties):
         return random.random()

cinder/scheduler/weights/volume_number.py

@@ -12,15 +12,6 @@
 #    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 #    License for the specific language governing permissions and limitations
 #    under the License.
-"""Weighers that weigh hosts by volume number in backends:
-
-1. Volume Number Weigher.  Weigh hosts by their volume number.
-
-The default is to spread volumes across all hosts evenly.  If you prefer
-stacking, you can set the 'volume_number_multiplier' option to a positive
-number and the weighing has the opposite effect of the default.
-"""
-
 
 from oslo_config import cfg
 
@@ -40,6 +31,13 @@ CONF.register_opts(volume_number_weight_opts)
 
 
 class VolumeNumberWeigher(weights.BaseHostWeigher):
+    """Weigher that weighs hosts by volume number in backends.
+
+    The default is to spread volumes across all hosts evenly. If you prefer
+    stacking, you can set the ``volume_number_multiplier`` option to a positive
+    number and the weighing has the opposite effect of the default.
+    """
+
     def weight_multiplier(self):
         """Override the weight multiplier."""
         return CONF.volume_number_multiplier

doc/source/database_architecture.rst

@@ -1,9 +0,0 @@
-==============================
- Cinder Database Architecture
-==============================
-
-Cinder Database Backends
-~~~~~~~~~~~~~~~~~~~~~~~~
-
-.. list-plugins:: cinder.database.migration_backend
-    :detailed:

doc/source/oslo-middleware.rst

@@ -1,6 +0,0 @@
-==========================
- Oslo Middleware
-==========================
-
-.. list-plugins:: oslo_middleware
-    :detailed: