Take out obsolete test that breaks the signal handlers

This test (test_explicit_loop_threaded) is added 7 years ago in #63
#63 in the good old days of
custom loops in libjuju. Nowadays everything's handled by the asyncio,
so I don't think anyone's using this library with a ThreadPoolExecutor
anymore.

The signal handlers are breaking because of a known issue from Python
3.8 python/cpython#78860.

Author: cderici

tests/integration/test_model.py

@@ -7,7 +7,6 @@
 import string
 import time
 import uuid
-from concurrent.futures import ThreadPoolExecutor
 
 import mock
 import paramiko
@@ -663,32 +662,6 @@ async def mock_AddRelation(*args, **kwargs):
         assert isinstance(my_relation, Relation)
 
 
-async def _deploy_in_loop(new_loop, model_name, jujudata):
-    new_model = Model(jujudata=jujudata)
-    await new_model.connect(model_name)
-    try:
-        await new_model.deploy('ubuntu', channel='stable')
-        assert 'ubuntu' in new_model.applications
-    finally:
-        await new_model.disconnect()
-
-
-@base.bootstrapped
-async def test_explicit_loop_threaded(event_loop):
-    async with base.CleanModel() as model:
-        model_name = model.name
-        new_loop = jasyncio.new_event_loop()
-        with ThreadPoolExecutor(1) as executor:
-            f = executor.submit(
-                new_loop.run_until_complete,
-                _deploy_in_loop(new_loop,
-                                model_name,
-                                model._connector.jujudata))
-            f.result()
-        await model._wait_for_new('application', 'ubuntu')
-        assert 'ubuntu' in model.applications
-
-
 @base.bootstrapped
 async def test_store_resources_charm(event_loop):
     pytest.skip('Revise: test_store_resources_charm intermittent test failure')