Harden `.ib.venues` against unknown exchange cals

Deats,
- catch `InvalidCalendarName` in `has_holiday()` so
  venues without an `exchange_calendars` entry (eg.
  `IDEALPRO` for forex, `PAXOS` for crypto) gracefully
  return `False` instead of raising.
- add `log` via `get_logger()` to emit a warning when
  skipping the holiday check for an unmapped venue.
- fix `std_exch` type annot from `dict` -> `str`.
- guard `is_expired()` against empty
  `.realExpirationDate` strings.
- fill in `is_expired()` docstring.

(this patch was generated in some part by [`claude-code`][claude-code-gh])
[claude-code-gh]: https://github.com/anthropics/claude-code

piker/brokers/ib/venues.py

@@ -33,6 +33,9 @@ from typing import (
 )
 
 import exchange_calendars as xcals
+from exchange_calendars.errors import (
+    InvalidCalendarName,
+)
 from pendulum import (
     parse,
     now,
@@ -41,6 +44,10 @@ from pendulum import (
     Time,
 )
 
+from piker.log import get_logger
+
+log = get_logger(__name__)
+
 if TYPE_CHECKING:
     from ib_async import (
         TradingSession,
@@ -61,10 +68,15 @@ def is_expired(
     con_deats: ContractDetails,
 ) -> bool:
     '''
-    Predicate 
+    Simple predicate whether the provided contract-deats match and
+    already lifetime-terminated instrument.
 
     '''
-    expiry_dt: datetime = parse(con_deats.realExpirationDate)
+    expiry_str: str = con_deats.realExpirationDate
+    if not expiry_str:
+        return False
+
+    expiry_dt: datetime = parse(expiry_str)
     return expiry_dt.date() >= now().date()
 
 
@@ -102,13 +114,28 @@ def has_holiday(
         con.exchange
     )
 
-    # XXX, ad-hoc handle any IB exchange which are non-std
-    # via lookup table..
-    std_exch: dict = {
+    # XXX, ad-hoc handle any IB exchange which are
+    # non-std via lookup table..
+    std_exch: str = {
         'ARCA': 'ARCX',
     }.get(exch, exch)
 
-    cal: ExchangeCalendar = xcals.get_calendar(std_exch)
+    try:
+        cal: ExchangeCalendar = xcals.get_calendar(
+            std_exch
+        )
+    except InvalidCalendarName:
+        # venue has no `exchange_calendars` entry
+        # (eg. IDEALPRO for forex, PAXOS for
+        # crypto) -> not a holiday by default since
+        # weekends are already handled by
+        # `has_weekend()`.
+        log.warning(
+            f'No exchange cal for {std_exch!r},'
+            f' skipping holiday check..\n'
+        )
+        return False
+
     end: datetime = period.end
     # _start: datetime = period.start
     # ?TODO, can rm ya?