Clean up babel.localtime (#952)

* Remove vestigial babel.localtime cache bits
* Give _FallbackLocalTimezone its own module

1 files changed, 9 insertions, 39 deletions

diff --git a/babel/localtime/__init__.py b/babel/localtime/__init__.py
index 1d65fb2..29577fa 100644
--- a/babel/localtime/__init__.py
+++ b/babel/localtime/__init__.py
@@ -11,8 +11,6 @@
 
 import datetime
 import sys
-import time
-from threading import RLock
 
 if sys.platform == 'win32':
     from babel.localtime._win32 import _get_localzone
@@ -20,43 +18,15 @@ else:
     from babel.localtime._unix import _get_localzone
 
 
-_cached_tz = None
-_cache_lock = RLock()
-
-STDOFFSET = datetime.timedelta(seconds=-time.timezone)
-if time.daylight:
-    DSTOFFSET = datetime.timedelta(seconds=-time.altzone)
-else:
-    DSTOFFSET = STDOFFSET
-
-DSTDIFF = DSTOFFSET - STDOFFSET
-ZERO = datetime.timedelta(0)
-
-
-class _FallbackLocalTimezone(datetime.tzinfo):
-
-    def utcoffset(self, dt: datetime.datetime) -> datetime.timedelta:
-        if self._isdst(dt):
-            return DSTOFFSET
-        else:
-            return STDOFFSET
-
-    def dst(self, dt: datetime.datetime) -> datetime.timedelta:
-        if self._isdst(dt):
-            return DSTDIFF
-        else:
-            return ZERO
-
-    def tzname(self, dt: datetime.datetime) -> str:
-        return time.tzname[self._isdst(dt)]
-
-    def _isdst(self, dt: datetime.datetime) -> bool:
-        tt = (dt.year, dt.month, dt.day,
-              dt.hour, dt.minute, dt.second,
-              dt.weekday(), 0, -1)
-        stamp = time.mktime(tt)
-        tt = time.localtime(stamp)
-        return tt.tm_isdst > 0
+# TODO(3.0): the offset constants are not part of the public API
+#            and should be removed
+from babel.localtime._fallback import (
+    DSTDIFF,  # noqa: F401
+    DSTOFFSET,  # noqa: F401
+    STDOFFSET,  # noqa: F401
+    ZERO,  # noqa: F401
+    _FallbackLocalTimezone,
+)
 
 
 def get_localzone() -> datetime.tzinfo: