fix: Wrap optional dependency in import guard

Author: lewisjared

changelog/297.fix.md

@@ -0,0 +1 @@
+Fix missing dependency in migrations

packages/climate-ref/src/climate_ref/migrations/env.py

@@ -1,4 +1,3 @@
-import alembic_postgresql_enum  # noqa
 from alembic import context, op
 from loguru import logger
 from sqlalchemy import Connection, inspect
@@ -9,6 +8,11 @@
 from climate_ref_core.logging import capture_logging
 from climate_ref_core.pycmec.controlled_vocabulary import CV
 
+try:
+    import alembic_postgresql_enum  # noqa
+except ImportError:
+    logger.warning("alembic_postgresql_enum not installed, skipping enum migration support")
+
 # Setup logging
 capture_logging()
 logger.debug("Running alembic env")