Remove ThreadPool with async executor (#4154)

* Remove ThreadPool with async executor

* Fix zigbee

* update unittest

* fix remote api

* add pending task to remote

* fix lint

* remove unused import

* remove old stuff for lazy tests

* fix bug and add a exception handler to executor

* change executor handling

* change to wait from gather

* fix unittest

tests/common.py

@@ -40,7 +40,6 @@ def get_test_home_assistant():
         loop = asyncio.new_event_loop()
 
     hass = loop.run_until_complete(async_test_home_assistant(loop))
-    hass.allow_pool = True
 
     # FIXME should not be a daemon. Means hass.stop() not called in teardown
     stop_event = threading.Event()
@@ -97,8 +96,6 @@ def async_test_home_assistant(loop):
 
     hass.state = ha.CoreState.running
 
-    hass.allow_pool = False
-
     # Mock async_start
     orig_start = hass.async_start
 
@@ -110,20 +107,6 @@ def async_test_home_assistant(loop):
 
     hass.async_start = mock_async_start
 
-    # Mock async_init_pool
-    orig_init = hass.async_init_pool
-
-    @ha.callback
-    def mock_async_init_pool():
-        """Prevent worker pool from being initialized."""
-        if hass.allow_pool:
-            with patch('homeassistant.core._async_monitor_worker_pool'):
-                orig_init()
-        else:
-            assert False, 'Thread pool not allowed. Set hass.allow_pool = True'
-
-    hass.async_init_pool = mock_async_init_pool
-
     return hass