[system] Don't use is_defined macro for system plugin entities.

It seems to clash with something and cause plugin actions to return
random `ImportError`.

platypush/entities/system.py

@@ -1,25 +1,19 @@
 from sqlalchemy import Boolean, Column, Float, ForeignKey, Integer, JSON, String
 
-from platypush.common.db import is_defined
-
 from . import Entity
 from .devices import Device
 from .sensors import NumericSensor, PercentSensor
 from .temperature import TemperatureSensor
 
 
-if not is_defined('cpu'):
+class Cpu(Entity):
-
-    class Cpu(Entity):
     """
     ``CPU`` ORM (container) model.
     """
 
     __tablename__ = 'cpu'
 
-        id = Column(
+    id = Column(Integer, ForeignKey(Entity.id, ondelete='CASCADE'), primary_key=True)
-            Integer, ForeignKey(Entity.id, ondelete='CASCADE'), primary_key=True
-        )
 
     percent = Column(Float)
 
@@ -29,18 +23,14 @@ if not is_defined('cpu'):
     }
 
 
-if not is_defined('cpu_info'):
+class CpuInfo(Entity):
-
-    class CpuInfo(Entity):
     """
     ``CpuInfo`` ORM model.
     """
 
     __tablename__ = 'cpu_info'
 
-        id = Column(
+    id = Column(Integer, ForeignKey(Entity.id, ondelete='CASCADE'), primary_key=True)
-            Integer, ForeignKey(Entity.id, ondelete='CASCADE'), primary_key=True
-        )
 
     architecture = Column(String)
     bits = Column(Integer)
@@ -61,18 +51,14 @@ if not is_defined('cpu_info'):
     }
 
 
-if not is_defined('cpu_times'):
+class CpuTimes(Entity):
-
-    class CpuTimes(Entity):
     """
     ``CpuTimes`` ORM (container) model.
     """
 
     __tablename__ = 'cpu_times'
 
-        id = Column(
+    id = Column(Integer, ForeignKey(Entity.id, ondelete='CASCADE'), primary_key=True)
-            Integer, ForeignKey(Entity.id, ondelete='CASCADE'), primary_key=True
-        )
 
     __table_args__ = {'extend_existing': True}
     __mapper_args__ = {
@@ -80,18 +66,14 @@ if not is_defined('cpu_times'):
     }
 
 
-if not is_defined('cpu_stats'):
+class CpuStats(Entity):
-
-    class CpuStats(Entity):
     """
     ``CpuStats`` ORM (container) model.
     """
 
     __tablename__ = 'cpu_stats'
 
-        id = Column(
+    id = Column(Integer, ForeignKey(Entity.id, ondelete='CASCADE'), primary_key=True)
-            Integer, ForeignKey(Entity.id, ondelete='CASCADE'), primary_key=True
-        )
 
     __table_args__ = {'extend_existing': True}
     __mapper_args__ = {
@@ -99,18 +81,14 @@ if not is_defined('cpu_stats'):
     }
 
 
-if not is_defined('memory_stats'):
+class MemoryStats(Entity):
-
-    class MemoryStats(Entity):
     """
     ``MemoryStats`` ORM model.
     """
 
     __tablename__ = 'memory_stats'
 
-        id = Column(
+    id = Column(Integer, ForeignKey(Entity.id, ondelete='CASCADE'), primary_key=True)
-            Integer, ForeignKey(Entity.id, ondelete='CASCADE'), primary_key=True
-        )
 
     total = Column(Integer)
     available = Column(Integer)
@@ -129,18 +107,14 @@ if not is_defined('memory_stats'):
     }
 
 
-if not is_defined('swap_stats'):
+class SwapStats(Entity):
-
-    class SwapStats(Entity):
     """
     ``SwapStats`` ORM model.
     """
 
     __tablename__ = 'swap_stats'
 
-        id = Column(
+    id = Column(Integer, ForeignKey(Entity.id, ondelete='CASCADE'), primary_key=True)
-            Integer, ForeignKey(Entity.id, ondelete='CASCADE'), primary_key=True
-        )
 
     total = Column(Integer)
     used = Column(Integer)
@@ -153,18 +127,14 @@ if not is_defined('swap_stats'):
     }
 
 
-if not is_defined('disk'):
+class Disk(Entity):
-
-    class Disk(Entity):
     """
     ``Disk`` ORM model.
     """
 
     __tablename__ = 'disk'
 
-        id = Column(
+    id = Column(Integer, ForeignKey(Entity.id, ondelete='CASCADE'), primary_key=True)
-            Integer, ForeignKey(Entity.id, ondelete='CASCADE'), primary_key=True
-        )
 
     mountpoint = Column(String)
     fstype = Column(String)
@@ -187,18 +157,14 @@ if not is_defined('disk'):
     }
 
 
-if not is_defined('network_interface'):
+class NetworkInterface(Device):
-
-    class NetworkInterface(Device):
     """
     ``NetworkInterface`` ORM model.
     """
 
     __tablename__ = 'network_interface'
 
-        id = Column(
+    id = Column(Integer, ForeignKey(Device.id, ondelete='CASCADE'), primary_key=True)
-            Integer, ForeignKey(Device.id, ondelete='CASCADE'), primary_key=True
-        )
 
     bytes_sent = Column(Integer)
     bytes_recv = Column(Integer)
@@ -220,9 +186,7 @@ if not is_defined('network_interface'):
     }
 
 
-if not is_defined('system_temperature'):
+class SystemTemperature(TemperatureSensor):
-
-    class SystemTemperature(TemperatureSensor):
     """
     Extends the ``TemperatureSensor``.
     """
@@ -244,9 +208,7 @@ if not is_defined('system_temperature'):
     }
 
 
-if not is_defined('system_fan'):
+class SystemFan(NumericSensor):
-
-    class SystemFan(NumericSensor):
     """
     ``SystemFan`` ORM model.
     """
@@ -265,9 +227,7 @@ if not is_defined('system_fan'):
     }
 
 
-if not is_defined('system_battery'):
+class SystemBattery(PercentSensor):
-
-    class SystemBattery(PercentSensor):
     """
     ``SystemBattery`` ORM model.
     """

platypush/plugins/system/__init__.py

@@ -634,6 +634,7 @@ class SystemPlugin(SensorPlugin, EntityManager):
                 if fan.get('id') and fan.get('label')
             ],
             *[
+                (
                     SystemBattery(
                         id='system:battery',
                         name='Battery',
@@ -641,6 +642,7 @@ class SystemPlugin(SensorPlugin, EntityManager):
                     )
                     if battery
                     else ()
+                )
             ],
         ]