Status beacon should raise proper exception

Also have it check for the status exec module in __virtual__()

salt/beacons/status.py

@@ -87,6 +87,7 @@ markers for specific list items:
 from __future__ import absolute_import
 import logging
 import datetime
+import salt.exceptions
 
 log = logging.getLogger(__name__)
 
@@ -99,6 +100,12 @@ def __validate__(config):
         return False, ('Configuration for status beacon must be a dictionary.')
     return True, 'Valid beacon configuration'
 
+def __virtual__():
+    # TODO Find a way to check the existence of the module itself, not just a single func
+    if 'status.w' not in __salt__:
+        return (False, 'The \'status\' execution module is not available on this system')
+    else:
+        return True
 
 def beacon(config):
     '''
@@ -118,7 +125,12 @@ def beacon(config):
 
     ret = {}
     for func in config:
-        data = __salt__['status.{0}'.format(func)]()
+        try:
+            data = __salt__['status.{0}'.format(func)]()
+        except salt.exceptions.NotImplemented as exc:
+            log.error('Status beacon attempted to process function {0} \
+                    but encountered error: {1}'.format(func, exc))
+            continue
         ret[func] = {}
         for item in config[func]:
             if item == 'all':

salt/modules/status.py

@@ -27,7 +27,7 @@ import salt.utils.event
 from salt.utils.network import host_to_ips as _host_to_ips
 from salt.utils.network import remote_port_tcp as _remote_port_tcp
 from salt.ext.six.moves import zip
-from salt.exceptions import CommandExecutionError
+from salt.exceptions import CommandExecutionError, NotImplemented
 
 __virtualname__ = 'status'
 __opts__ = {}
@@ -210,8 +210,14 @@ def loadavg():
     .. code-block:: bash
 
         salt '*' status.loadavg
+
+        :raises NotImpelemnted: If the system cannot report loadaverages to Python
     '''
-    load_avg = os.getloadavg()
+    try:
+        load_avg = os.getloadavg()
+    except AttributeError:
+        # Some UNIX-based operating systems do not have os.getloadavg()
+        raise salt.exceptions.CommandExecutionError('status.loadavag is not available on your platform')
     return {'1-min': load_avg[0],
             '5-min': load_avg[1],
             '15-min': load_avg[2]}