refactor: add common base class to GitHubClient and LocalClient

Enables adding type checking to minimize mypy errors

Client.py

@@ -0,0 +1,12 @@
+class Client(object):
+    def get_last_diff(self):
+        return None
+
+    def create_issue(self, issue):
+        return [201, None]
+
+    def close_issue(self, issue):
+        return 200
+
+    def get_issue_url(self, new_issue_number):
+        return "N/A"

GitHubClient.py

@@ -1,8 +1,9 @@
 import os
 import requests
 import json
+from Client import Client
 
-class GitHubClient(object):
+class GitHubClient(Client):
     """Basic client for getting the last diff and managing issues."""
     existing_issues = []
     milestones = []

LocalClient.py

@@ -1,7 +1,8 @@
 import subprocess
 import os
+from Client import Client
 
-class LocalClient(object):
+class LocalClient(Client):
     def __init__(self):
         self.diff_url = None
         self.commits = ['placeholder'] # content doesn't matter, just length
@@ -31,12 +32,3 @@ class LocalClient(object):
 
     def get_last_diff(self):
         return subprocess.run(['git', 'diff', f'{self.base_ref}..{self.sha}'], stdout=subprocess.PIPE).stdout.decode('latin-1')
-
-    def create_issue(self, issue):
-        return [201, None]
-
-    def close_issue(self, issue):
-        return 200
-
-    def get_issue_url(self, new_issue_number):
-        return "N/A"

main.py

@@ -10,18 +10,20 @@ import operator
 from collections import defaultdict
 from TodoParser import TodoParser
 from LineStatus import LineStatus
+from Client import Client
 from LocalClient import LocalClient
 from GitHubClient import GitHubClient
 
 
 if __name__ == "__main__":
+    client: Client | None = None
     # Try to create a basic client for communicating with the remote version control server, automatically initialised with environment variables.
     try:
         # try to build a GitHub client
         client = GitHubClient()
     except EnvironmentError:
         # don't immediately give up
-        client = None
+        pass
     # if needed, fall back to using a local client for testing
     client = client or LocalClient()