core: cleanup deprecations, exclude from type checking and show runtime warnings

among affected things:

- core.common.assert_never
- core.common.cproperty
- core.common.isoparse
- core.common.mcachew
- core.common.the
- core.common.tzdatetime
- core.compat.sqlite_backup

my/time/tz/common.py

@@ -1,7 +1,7 @@
 from datetime import datetime
-from typing import Callable, cast
+from typing import Callable, Literal, cast
 
-from ...core.common import tzdatetime, Literal
+from my.core.common import datetime_aware
 
 
 '''
@@ -30,7 +30,11 @@ def default_policy() -> TzPolicy:
         return 'keep'
 
 
-def localize_with_policy(lfun: Callable[[datetime], tzdatetime], dt: datetime, policy: TzPolicy=default_policy()) -> tzdatetime:
+def localize_with_policy(
+    lfun: Callable[[datetime], datetime_aware],
+    dt: datetime,
+    policy: TzPolicy=default_policy()
+) -> datetime_aware:
     tz = dt.tzinfo
     if tz is None:
         return lfun(dt)

my/time/tz/main.py

@@ -2,10 +2,10 @@
 Timezone data provider, used to localize timezone-unaware timestamps for other modules
 '''
 from datetime import datetime
-from ...core.common import tzdatetime
+from my.core.common import datetime_aware
 
 # todo hmm, kwargs isn't mypy friendly.. but specifying types would require duplicating default args. uhoh
-def localize(dt: datetime, **kwargs) -> tzdatetime:
+def localize(dt: datetime, **kwargs) -> datetime_aware:
     # todo document patterns for combining multiple data sources
     # e.g. see https://github.com/karlicoss/HPI/issues/89#issuecomment-716495136
     from . import via_location as L

my/time/tz/via_location.py

@@ -17,8 +17,8 @@ from typing import Iterator, Optional, Tuple, Any, List, Iterable, Set, Dict
 
 import pytz
 
+from my.core.cachew import mcachew
 from my.core import make_logger, stat, Stats, datetime_aware
-from my.core.common import mcachew
 from my.core.source import import_source
 from my.core.warnings import high