Run lint CI job and Ubuntu 22.04 and 18.04 (#1505)

* Run lint CI job and Ubuntu 22.04 and 18.04

* Fix lint errors

.github/workflows/lint.yml

@@ -3,7 +3,12 @@ on: [push, pull_request]
 
 jobs:
   lint:
-    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        # Only care about the oldest and newest versions
+        os: [ubuntu-22.04, ubuntu-18.04]
+    runs-on: ${{ matrix.os }}
     timeout-minutes: 10
     steps:
     - uses: actions/checkout@v3
@@ -13,11 +18,6 @@ jobs:
         path: ~/.cache/pip
         key: ${{ matrix.os }}-cache-pip
 
-    - name: Set up Python 3.8
-      uses: actions/setup-python@v4
-      with:
-        python-version: 3.8
-
     - name: Install dependencies
       run: |
         ./setup.sh --user

pwndbg/heap/ptmalloc.py

@@ -5,7 +5,7 @@ from enum import Enum
 from typing import Any
 from typing import Dict
 from typing import Set
-from typing import Union
+from typing import Union  # noqa: F401
 
 import gdb
 

pwndbg/lib/memoize.py

@@ -10,7 +10,7 @@ from collections.abc import Hashable
 from typing import Any
 from typing import Callable
 from typing import Dict
-from typing import List
+from typing import List  # noqa: F401
 
 debug = False