Fix ignores in test_{scanner,file_downloader}.py

python/mypy#2427 (comment)
describes the mypy change, in mypy 1.1.0

Author: David Robertson

tests/scanner/test_file_downloader.py

@@ -64,7 +64,7 @@ async def _get(
 
         # Mock _get so we don't actually try to download files.
         self.get_mock = Mock(side_effect=_get)
-        self.downloader._get = self.get_mock  # type: ignore[assignment]
+        self.downloader._get = self.get_mock  # type: ignore[method-assign]
 
     async def test_download(self) -> None:
         """Tests that downloading a file works."""
@@ -230,7 +230,7 @@ async def _get(
 
         # Mock _get so we don't actually try to download files.
         self.get_mock = Mock(side_effect=_get)
-        self.downloader._get = self.get_mock  # type: ignore[assignment]
+        self.downloader._get = self.get_mock  # type: ignore[method-assign]
 
     async def test_discover(self) -> None:
         """Checks that the base URL to use to download files can be discovered via

tests/scanner/test_scanner.py

@@ -52,7 +52,7 @@ async def download_file(
 
         # Mock download_file so we don't actually try to download files.
         mcs = get_content_scanner()
-        mcs.file_downloader.download_file = self.downloader_mock  # type: ignore[assignment]
+        mcs.file_downloader.download_file = self.downloader_mock  # type: ignore[method-assign]
         self.scanner = mcs.scanner
 
     async def test_scan(self) -> None:
@@ -161,7 +161,7 @@ async def test_cache_max_size_mismatching_hash(self) -> None:
         """
         # Mock the _run_scan command so we can keep track of its call count.
         mock_runner = Mock(return_value=0)
-        self.scanner._run_scan = mock_runner  # type: ignore[assignment]
+        self.scanner._run_scan = mock_runner  # type: ignore[method-assign]
 
         # Calculate the cache key for this file so we can look it up later.
         cache_key = self.scanner._get_cache_key_for_file(MEDIA_PATH, None, None)
@@ -269,7 +269,7 @@ async def test_dont_cache_exit_codes(self) -> None:
         # It's tricky to give a value to `scanner._script` that makes `_run_scan` return 5
         # directly, so we just mock it here.
         run_scan_mock = Mock(return_value=5)
-        self.scanner._run_scan = run_scan_mock  # type: ignore[assignment]
+        self.scanner._run_scan = run_scan_mock  # type: ignore[method-assign]
 
         # Scan the file, we'll check later that it wasn't cached.
         with self.assertRaises(FileDirtyError):
@@ -318,7 +318,7 @@ async def _scan_file(*args: Any) -> MediaDescription:
             return self.downloader_res
 
         scan_mock = Mock(side_effect=_scan_file)
-        self.scanner._scan_file = scan_mock  # type: ignore[assignment]
+        self.scanner._scan_file = scan_mock  # type: ignore[method-assign]
 
         # Request two scans of the same file at the same time.
         results = await asyncio.gather(