Use encoding option or binary mode for open()

src/pip/_internal/operations/install/wheel.py

@@ -766,7 +766,7 @@ def _install_wheel(
     # Record the REQUESTED file
     if requested:
         requested_path = os.path.join(dest_info_dir, 'REQUESTED')
-        with open(requested_path, "w"):
+        with open(requested_path, "wb"):
             pass
         generated.append(requested_path)
 

src/pip/_internal/req/req_tracker.py

@@ -113,7 +113,7 @@ class RequirementTracker:
         assert req not in self._entries
 
         # Start tracking this requirement.
-        with open(entry_path, 'w') as fp:
+        with open(entry_path, 'w', encoding="utf-8") as fp:
             fp.write(str(req))
         self._entries.add(req)
 

src/pip/_internal/self_outdated_check.py

@@ -48,7 +48,7 @@ class SelfCheckState:
                 cache_dir, "selfcheck", _get_statefile_name(self.key)
             )
             try:
-                with open(self.statefile_path) as statefile:
+                with open(self.statefile_path, encoding="utf-8") as statefile:
                     self.state = json.load(statefile)
             except (OSError, ValueError, KeyError):
                 # Explicitly suppressing exceptions, since we don't want to