Replacing tempfile with mock_open in tests (#3753)

- test_bootstrap.py
- test_config.py
- components/test_init.py
- components/test_panel_custom.py
- components/test_api.py
- components/notify/test_file.py
- components/notify/test_demo.py
- components/camera/test_local_file.py
- helpers/test_config_validation.py
- util/test_package.py
- util/test_yaml.py

No changes needed in:
- components/cover/test_command_line.py
- components/switch/test_command_line.py
- components/rollershutter/test_command_line.py
- components/test_shell_command.py
- components/notify/test_command_line.py

Misc changes in:
- components/mqtt/test_server.py

Also, removed some unused mock parameters in tests/components/mqtt/test_server.py.

tests/components/camera/test_local_file.py

@@ -1,5 +1,4 @@
 """The tests for local file camera component."""
-from tempfile import NamedTemporaryFile
 import unittest
 from unittest import mock
 
@@ -26,45 +25,46 @@ class TestLocalCamera(unittest.TestCase):
 
     def test_loading_file(self):
         """Test that it loads image from disk."""
+        test_string = 'hello'
         self.hass.wsgi = mock.MagicMock()
 
-        with NamedTemporaryFile() as fptr:
-            fptr.write('hello'.encode('utf-8'))
-            fptr.flush()
-
+        with mock.patch('os.path.isfile', mock.Mock(return_value=True)), \
+                mock.patch('os.access', mock.Mock(return_value=True)):
             assert setup_component(self.hass, 'camera', {
                 'camera': {
                     'name': 'config_test',
                     'platform': 'local_file',
-                    'file_path': fptr.name,
+                    'file_path': 'mock.file',
                 }})
 
-            image_view = self.hass.wsgi.mock_calls[0][1][0]
+        image_view = self.hass.wsgi.mock_calls[0][1][0]
 
+        m_open = mock.mock_open(read_data=test_string)
+        with mock.patch(
+                'homeassistant.components.camera.local_file.open',
+                m_open, create=True
+        ):
             builder = EnvironBuilder(method='GET')
             Request = request_class()  # pylint: disable=invalid-name
             request = Request(builder.get_environ())
             request.authenticated = True
             resp = image_view.get(request, 'camera.config_test')
 
-            assert resp.status_code == 200, resp.response
-            assert resp.response[0].decode('utf-8') == 'hello'
+        assert resp.status_code == 200, resp.response
+        assert resp.response[0].decode('utf-8') == test_string
 
     def test_file_not_readable(self):
         """Test local file will not setup when file is not readable."""
         self.hass.wsgi = mock.MagicMock()
 
-        with NamedTemporaryFile() as fptr:
-            fptr.write('hello'.encode('utf-8'))
-            fptr.flush()
+        with mock.patch('os.path.isfile', mock.Mock(return_value=True)), \
+                mock.patch('os.access', return_value=False), \
+                assert_setup_component(0):
+            assert setup_component(self.hass, 'camera', {
+                'camera': {
+                    'name': 'config_test',
+                    'platform': 'local_file',
+                    'file_path': 'mock.file',
+                }})
 
-            with mock.patch('os.access', return_value=False), \
-                    assert_setup_component(0):
-                assert setup_component(self.hass, 'camera', {
-                    'camera': {
-                        'name': 'config_test',
-                        'platform': 'local_file',
-                        'file_path': fptr.name,
-                    }})
-
-                assert [] == self.hass.states.all()
+            assert [] == self.hass.states.all()