general: initial flake8 checks (for now manual)

fix fairly uncontroversial stuff in my.core like
- line spacing, which isn't too annoying (e.g. unlike many inline whitespace checks that break vertical formatting)
- unused imports/variables
- too broad except

my/core/__init__.py

@@ -1,6 +1,6 @@
 # this file only keeps the most common & critical types/utility functions
-from .common import PathIsh, Paths, Json
-from .common import get_files
+from .common import get_files, PathIsh, Paths
+from .common import Json
 from .common import LazyLogger
 from .common import warn_if_empty
 from .common import stat, Stats
@@ -8,11 +8,32 @@ from .common import datetime_naive, datetime_aware
 from .common import assert_never
 
 from .cfg import make_config
+
 from .util import __NOT_HPI_MODULE__
 
 from .error import Res, unwrap
 
 
 # just for brevity in modules
+# todo not sure about these.. maybe best to rely on regular imports.. perhaps compare?
 from dataclasses import dataclass
 from pathlib import Path
+
+
+__all__ = [
+    'get_files', 'PathIsh', 'Paths',
+    'Json',
+    'LazyLogger',
+    'warn_if_empty',
+    'stat', 'Stats',
+    'datetime_aware', 'datetime_naive',
+    'assert_never',
+
+    'make_config',
+
+    '__NOT_HPI_MODULE__',
+
+    'Res', 'unwrap',
+
+    'dataclass', 'Path',
+]