Async bootstrap / component init (#3991)

* Async bootstrap

* Adress comments

* Fix tests

* More fixes

* Tests fixes

tests/scripts/test_check_config.py

@@ -3,7 +3,6 @@ import asyncio
 import logging
 import os
 import unittest
-from unittest.mock import patch
 
 import homeassistant.scripts.check_config as check_config
 from tests.common import patch_yaml_files, get_test_config_dir
@@ -45,12 +44,22 @@ def tearDownModule(self):  # pylint: disable=invalid-name
         os.remove(path)
 
 
-@patch('asyncio.get_event_loop', return_value=asyncio.new_event_loop())
 class TestCheckConfig(unittest.TestCase):
     """Tests for the homeassistant.scripts.check_config module."""
 
+    def setUp(self):
+        """Prepare the test."""
+        # Somewhere in the tests our event loop gets killed,
+        # this ensures we have one.
+        try:
+            asyncio.get_event_loop()
+        except (RuntimeError, AssertionError):
+            # Py35: RuntimeError
+            # Py34: AssertionError
+            asyncio.set_event_loop(asyncio.new_event_loop())
+
     # pylint: disable=no-self-use,invalid-name
-    def test_config_platform_valid(self, mock_get_loop):
+    def test_config_platform_valid(self):
         """Test a valid platform setup."""
         files = {
             'light.yaml': BASE_CONFIG + 'light:\n  platform: demo',
@@ -66,7 +75,7 @@ class TestCheckConfig(unittest.TestCase):
                 'yaml_files': ['.../light.yaml']
             }, res)
 
-    def test_config_component_platform_fail_validation(self, mock_get_loop):
+    def test_config_component_platform_fail_validation(self):
         """Test errors if component & platform not found."""
         files = {
             'component.yaml': BASE_CONFIG + 'http:\n  password: err123',
@@ -104,7 +113,7 @@ class TestCheckConfig(unittest.TestCase):
             self.assertDictEqual({}, res['secrets'])
             self.assertListEqual(['.../platform.yaml'], res['yaml_files'])
 
-    def test_component_platform_not_found(self, mock_get_loop):
+    def test_component_platform_not_found(self):
         """Test errors if component or platform not found."""
         files = {
             'badcomponent.yaml': BASE_CONFIG + 'beer:',
@@ -131,7 +140,7 @@ class TestCheckConfig(unittest.TestCase):
             self.assertDictEqual({}, res['secrets'])
             self.assertListEqual(['.../badplatform.yaml'], res['yaml_files'])
 
-    def test_secrets(self, mock_get_loop):
+    def test_secrets(self):
         """Test secrets config checking method."""
         files = {
             get_test_config_dir('secret.yaml'): (