Add test to verify support for non-utf8 Python files

While it's recommended to encode Python files in UTF8, we should support
alternative encodings.

Author: seddonym

tests/assets/encodingpackage/shift_jis_importer.py

@@ -1,2 +1,3 @@
-# This file is encoded in shift_jis
-from .imported import ƒÎ
+# -*- coding: shift_jis -*-
+
+from .imported import ƒÎ

tests/functional/test_encoding_handling.py

@@ -32,10 +32,10 @@ def test_build_graph_of_non_utf8_source():
     )
 
     assert [
-               {
-                   "importer": "encodingpackage.shift_jis_importer",
-                   "imported": "encodingpackage.imported",
-                   "line_number": 2,
-                   "line_contents": "from .imported import π",
-               },
-           ] == result
+        {
+            "importer": "encodingpackage.shift_jis_importer",
+            "imported": "encodingpackage.imported",
+            "line_number": 3,
+            "line_contents": "from .imported import π",
+        },
+    ] == result