dhcp: fix linter, more TimeoutError fixes (?) for older pythons

pyroute2/dhcp/client.py

@@ -151,8 +151,8 @@ async def wait_for_state(
         '''Waits until the client is in the target state.'''
         try:
             await asyncio.wait_for(self._states[state].wait(), timeout=timeout)
-        except TimeoutError as err:
-            raise TimeoutError(
+        except asyncio.exceptions.TimeoutError as err:
+            raise asyncio.exceptions.TimeoutError(
                 f'Timed out waiting for the {state.name} state. '
                 f'Current state: {self.state.name}'
             ) from err

tests/test_linux/test_dhcp/test_integration.py

@@ -1,6 +1,6 @@
 import json
-from ipaddress import IPv4Address
 import os
+from ipaddress import IPv4Address
 from pathlib import Path
 
 import pytest