get elb helpers shouldn't raise if none elbs exist. (#238)

* get elb helpers shouldn't raise if none elbs exist.

* Remove offending test as well.

bootstrap_cfn/fab_tasks.py

@@ -990,22 +990,18 @@ def get_public_elbs(f=None):
     """
     Returns a list of internet-facing ELBs from the CloudFormation
     configuration containing items for which the filter function f
-    returns True, or everything. Raises an error if the list is empty.
+    returns True, or everything. or None if empty.
     """
     elbs = get_all_elbs(f)
-    if len(elbs) < 1:
-        raise PublicELBNotFoundError
     return elbs
 
 
 def get_first_public_elb():
     """
-    Returns the first public ELB if exists, or raise an error.
+    Returns the first public ELB if exists or None.
     """
     elbs = get_all_elbs()
-    if len(elbs) < 1:
-        raise PublicELBNotFoundError
-    return elbs[0]
+    return next(iter(elbs), None)
 
 
 @task

tests/test_fab_tasks.py

@@ -178,17 +178,6 @@ def test_get_first_public_elb(self, get_all_elbs_function):
         first_elb = fab_tasks.get_first_public_elb()
         self.assertEqual(first_elb, "unittest_elb")
 
-    @patch('bootstrap_cfn.fab_tasks.get_all_elbs', return_value=[])
-    def test_no_public_elb(self, get_all_elbs_function):
-        '''
-        Check if exception is raised when no elbs found
-        Args:
-            get_all_elbs_function: mock of get_all_elbs(), a list of elbs
-
-        '''
-        with self.assertRaises(errors.PublicELBNotFoundError):
-            fab_tasks.get_first_public_elb()
-
     @patch('bootstrap_cfn.fab_tasks.get_connection')
     @patch('bootstrap_cfn.fab_tasks.get_zone_name', return_value="dsd.io")
     @patch('bootstrap_cfn.fab_tasks.get_legacy_name', return_value="unittest-dev")