Fix invalid date entering cache DB

'peewee.DateTimeField' is not ISO-compliant. If user enforces strict ISO-compliance,
then translation between DateTimeField and sqlite breaks. Fix is to manually
implement translation.

yfinance/cache.py

@@ -197,17 +197,6 @@ def get_tz_cache():
     return _TzCacheManager.get_tz_cache()
 
 
-def set_tz_cache_location(cache_dir: str):
-    """
-    Sets the path to create the "py-yfinance" cache folder in.
-    Useful if the default folder returned by "appdir.user_cache_dir()" is not writable.
-    Must be called before cache is used (that is, before fetching tickers).
-    :param cache_dir: Path to use for caches
-    :return: None
-    """
-    _TzDBManager.set_location(cache_dir)
-
-
 
 # --------------
 # Cookie cache
@@ -300,9 +289,21 @@ def get_location(cls):
 
 
 Cookie_db_proxy = _peewee.Proxy()
+class ISODateTimeField(_peewee.DateTimeField):
+    # Ensure Python datetime is read & written correctly for sqlite, 
+    # because user discovered peewee allowed an invalid datetime
+    # to get written.
+    def db_value(self, value):
+        if value and isinstance(value, _datetime.datetime):
+            return value.isoformat()
+        return super().db_value(value)
+    def python_value(self, value):
+        if value and isinstance(value, str) and 'T' in value:
+            return _datetime.datetime.fromisoformat(value)
+        return super().python_value(value)
 class _CookieSchema(_peewee.Model):
     strategy = _peewee.CharField(primary_key=True)
-    fetch_date = _peewee.DateTimeField(default=_datetime.datetime.now)
+    fetch_date = ISODateTimeField(default=_datetime.datetime.now)
 
     # Which cookie type depends on strategy
     cookie_bytes = _peewee.BlobField()
@@ -398,3 +399,19 @@ def store(self, strategy, cookie):
 def get_cookie_cache():
     return _CookieCacheManager.get_cookie_cache()
 
+
+
+def set_cache_location(cache_dir: str):
+    """
+    Sets the path to create the "py-yfinance" cache folder in.
+    Useful if the default folder returned by "appdir.user_cache_dir()" is not writable.
+    Must be called before cache is used (that is, before fetching tickers).
+    :param cache_dir: Path to use for caches
+    :return: None
+    """
+    _TzDBManager.set_location(cache_dir)
+    _CookieDBManager.set_location(cache_dir)
+
+def set_tz_cache_location(cache_dir: str):
+    set_cache_location(cache_dir)
+