Upgrade flake8 to 3.8.1, fix findings (#35578)

.pre-commit-config.yaml

@@ -22,7 +22,7 @@ repos:
           - --quiet-level=2
         exclude_types: [csv, json]
   - repo: https://gitlab.com/pycqa/flake8
-    rev: 3.7.9
+    rev: 3.8.1
     hooks:
       - id: flake8
         additional_dependencies:

homeassistant/components/hunterdouglas_powerview/__init__.py

@@ -124,7 +124,7 @@ async def async_setup_entry(hass: HomeAssistant, entry: ConfigEntry):
         async with async_timeout.timeout(10):
             shade_entries = await shades.get_resources()
         if not shade_entries:
-            raise UpdateFailed(f"Failed to fetch new shade data.")
+            raise UpdateFailed("Failed to fetch new shade data.")
         return _async_map_data_by_id(shade_entries[SHADE_DATA])
 
     coordinator = DataUpdateCoordinator(

requirements_test_pre_commit.txt

@@ -4,7 +4,7 @@ bandit==1.6.2
 black==19.10b0
 codespell==1.16.0
 flake8-docstrings==1.5.0
-flake8==3.7.9
+flake8==3.8.1
 isort==4.3.21
 pydocstyle==5.0.2
 pyupgrade==2.3.0

tests/components/zwave_mqtt/conftest.py

@@ -12,13 +12,13 @@ from tests.common import load_fixture
 @pytest.fixture(name="generic_data", scope="session")
 def generic_data_fixture():
     """Load generic MQTT data and return it."""
-    return load_fixture(f"zwave_mqtt/generic_network_dump.csv")
+    return load_fixture("zwave_mqtt/generic_network_dump.csv")
 
 
 @pytest.fixture(name="light_data", scope="session")
 def light_data_fixture():
     """Load light dimmer MQTT data and return it."""
-    return load_fixture(f"zwave_mqtt/light_network_dump.csv")
+    return load_fixture("zwave_mqtt/light_network_dump.csv")
 
 
 @pytest.fixture(name="sent_messages")